@anny89,
It's good to hear that it's a first. If it helps...it may be a one off caused by your comments to her mother. Many people are VERY protective of their mothers...well, I'm only speaking for guys really, but I'm guessing that women can be that way also.
As for the age difference, it means a lot more that what you think, regardless of what she tells you.
- She called you a brat - brat is a derogaratory nickname for children.
- She spanked you - that's only something you do to kids, or in kinky sex games (and you said it wasn't the latter, so it's something you do to a child)
Also, as you age, many of your priorities change, and your view of life and events change. For example :
- when you get to 40, you may maybe 20-30 years working life left in front of you. You no longer have all the time in the world to think about retirement, and you need to start working towards it
- if you want children and haven't had them, your time to have them grows shorter and shorter
- you start thinking more about how to use your time, what you want out of life, and how to achieve it (people who have a midlife crisis suddenly realise they haven't been doing any of this)
- you've learnt a lot more about life
- the topics you like to talk about change
- your body starts getting aches and pains it never had, and becomes less capable
- it becomes harder to keep the weight off
- you become more fearful (of making a fool of yourself, of not being able to do things, of trying dangerous things / new difficult things, etc)
- your prefered ways of 'partying' change.
Now obviously, all the above doesn't apply to everyone, and some points will mean more or less than others to various people. I've even left lots of other differences out I'm sure - for those are just the ones I can think of off the top of my head.
The point is - the difference between 20 years of age, and 40 years of age is vast, no matter that anyone wants to pretend otherwise.