am i in the wrong?

It seems from what you wrote...that you can't convince her for some reason. I'm not sure about this business about making practical jokes. not sure who or how that got started but that had better stop.

She's seems to be paranoid and has abandonment issues. Have you ever cheated on her? Has someone else ever cheated on her?

You need to encourage her in as many ways possible and be supportive. If you are doing that already...you need to talk this out with her and tell her she needs. I can't understand logically why she would feel threatened after that practical joke about you being fired. That made no sense at all. Perhaps, this is just her paranoia working overtime?

This cousin or cousin's g/f should find real ways to verbally reassure your g/f and never mind these practical jokes. Something is missing from this story.

However, it does seem your g/f needs counseling. That might be the best route to go.

Yes she has been cheated on in the past, if im honest I think im the only relationship she has had where she hasn't been cheated on, I reassure her that im not like that, she knows I love her. As for the practical joke, im not sure why it was thought to be amusing, that or me and my girlfriend don't have that kind of a sense of humour anyway that was instantly stopped, I was thinking about getting them both together but with how my girlfriend is currently acting I don't think that would be for the best just yet, I just dint know what else I can do...

Oh come on, now.
You are a big boy - father, wage earner, long time relationship.
You know how to put the skids on a "friendship" that has threatened all this.
Cut back on the "friendship" with this other gal. Find a male buddy to hang and joke with.

That "joke" was way out of line and almost passive-aggressive in nature.

PS any reason why you aren't married to the woman who has two of your children - or are they not yours?

You put some very good points across but is that really what it takes to make a relationship, sacrifice any friendship with any other woman i come across? That doesn't exactly seem fair. Also we was planning to get married, i just don't understand how after 5 years she doesn't seem to be able to trust me. Is it really me? Am i really in the wrong for having a female friend?

A unknown, single, female friend who calls your house and plays a joke on you and your wife that you got fired?

I'll wait for others to chime in but that wouldn't fly with me.

Put this in its place.

That's the thing, she's not a random unknown female, my girlfriend knows her

So? Perhaps you need to put aside this female 'friend' in order to make the woman you love and have children with to feel more secure.

Question: is she like this about any other female? I'll bet she's not!

No, you are not wrong.

To add to my reply, love doesn't mean smothering someone.

Do you want to worry about not being friendly to other women for the rest of your life? Jealousy can be a wretched problem for both parties.
I would strongly advise not marrying until you two work this out - and not by way of your promising to have no female friends forever.

There's an old book by Kahlil Gibran (a lebanese american artist and poet born in 1883) that was popular in my younger days and may still be, for all I know. Title - the prophet.
He has wise things to say about relationships.

Here's one -

On Marriage

Then Almitra spoke again and said, "And what of Marriage, master?"
And he answered saying:
You were born together, and together you shall be forevermore.
You shall be together when white wings of death scatter your days.
Aye, you shall be together even in the silent memory of God.
But let there be spaces in your togetherness,
And let the winds of the heavens dance between you.
Love one another but make not a bond of love:
Let it rather be a moving sea between the shores of your souls.
Fill each other's cup but drink not from one cup.
Give one another of your bread but eat not from the same loaf.
Sing and dance together and be joyous, but let each one of you be alone,
Even as the strings of a lute are alone though they quiver with the same music.
Give your hearts, but not into each other's keeping.
For only the hand of Life can contain your hearts.
And stand together, yet not too near together:
For the pillars of the temple stand apart,
And the oak tree and the cypress grow not in each other's shadow.


Source: http://www-personal.umich.edu/~jrcole/gibran/prophet/prophet.htm#Marriage

But she is! Not to the same extent as she is at the moment but every time I talk to a female she is always highly questionable and you can tell from get tone she has a real problem with it, I do get what you mean, put the breaks on the friendship but how do I do that without coming across as an asshole, I can't say "I can't talk to you anymore, my girlfriend thinks im cheating on her with you" because that might not only cause problems in her relationship but also in the family. Is there any way this can be done?

You know what, thank you, I didn't think I was wrong to have a female friend, I have been feeling like **** about this all week not sure weather I have something to apologise for or not, I really like the quote from the book, I like what you mean by it and I think I will read it to my girlfriend and she if she understands what it means and what she thinks about it. Thank you.

I've worked with a lot of Lesbians over the years. In one case about 4 years ago, I worked with 3 of them...they were all in long term relationships with the female partners. Let's call my 3 Lesbian colleagues B, C & D ('A' is problematic)

B started having an affair with C
B also started having an affair with D

...neither C nor D knew that B was having an affair with both of them (and remember they still all had long term partners).

They suddenly all found out. C blamed D (as if that somehow made any sense at all), and D blamed B (a little more sensible), but in all of it B came out with little to no problems, while D was ostracised by the other women in the place (the guys didn't care), and C people were a little wary of for a while.

Others have stated outright that the Lesbian world is very, err...promiscuous (much more so than the hetero sexual world it seems).

And so it seems that they feel much less secure in their relationships than their male/female couple versions.

That's a generalisation - but reading the OP - it reminded me so much of such things.