Did I blow things out of proportion?

How big is the park that it matters exactly where you would be meeting?

Couldn't you have gone to the park and then walked to the meeting point? or gone to the park and hoped to run into your friend by chance?

If it would take several hours to walk across the park if I'd guessed the wrong meeting point, I might get the point of being annoyed, but really, no.

So why didn't you show up for the party?

They ended up in the park, right?

I can't say for sure whether you overreacted. There was definitely a lack of communication and organization, which would indeed cause an invited guest to become frustrated. Whether she was offended or not, I think your friend ought to realize that informing you of the designated meeting point only two minutes before you're scheduled to be there was unacceptable on her part. If she didn't immediately apologize when you informed her of your frustration and ask you to please come despite the disorganization of her event, then I wouldn't spend too much time agonizing over the matter.

Yes, that is definitely a factor. There are some parks in my community that are very large, and others that are very small. If my invitation says, please come to my child's birthday party at such & such small community playground park, the precise location would be irrelevant because the entire park can be seen as one drives into the parking lot. The larger parks might be a little more problematic to search for the location of a party group if I didn't know approximately where to start looking. If I lived in NYC and was asked to attend a party in Central Park (843 acres; 53 miles of pedestrian paths), I would desire the invitation to include an exact location.

funny - Central Park was what I was thinking of - I consider it walkable and would take the opportunity to just spend time there if I didn't have the exact location

I've never been there myself. But for my ill health, I would also love to take a walking tour and explore the park.

You might have - it kind of depends on the circumstances. For example if it wasn't set in stone where they were going to meet - maybe that is why she didn't text you until the last minute. Maybe she just assumed that everyone would think directly in front made sense? Is the metro very close to the park so it isn't really an inconvenience? Or maybe a last minute change of plans for some reason - did you ask her why she didn't let you know earlier?

(this is just from what I can read here so I am making many assumptions) My take - she probably isn't the best organizer and probably flies by the seat of her pants - perhaps that is why you tried to nail her down to a specific spot knowing the way she is. She may have been trying to get a consensus from the other party goers or maybe as she was coming out of the metro she bumped into many of the invitees so it just made sense to text the few others to just meet there.

There could be many reasons why the last minute text - but if this was an informal get together and the change in location wasn't such that it was a hassle --- you had to drive or it took 20 minutes to walk from your previous location - what is really the big deal? They weren't going to leave without you if you were 5 minutes later?

I know she should have let you know earlier and you were trying to be organized, but if she is the type that is not organized like you, you kind of need to realize that and don't take it personally.

Now if it caused you the cost of a cab ride or another trip on the metro I can understand the frustration, but if it was just a walk around the corner, then I think you might have overreacted.