People say that because they want to be nice. But it's hard for people to understand when someone thinks and feels significantly differently than they do.
So it might be useful to think of it as, "this person hopes I have a positive experience." They say it in a way that makes sense to them, and they don't realize that you think of things differently.
So when they say "do something you like," think of it as them saying "I hope you do something that makes you feel good." You may not "like" things the way most people do, but you can still feel good about things - even if it's an intellectual "this is positive," as opposed to an emotional "I'm doing something that makes me feel happy."
It would also be interesting if she doesn't quite "get" gender in general.
Like, if she meets a stereotypical dudebro who most folks would think is obviously presenting male, she'd ask him his pronouns. And if someone said to her he's obviously a guy, she wouldn't understand why they assume that.
Not trying to write your story for you, it's just something that came to mind after I replied. :)
I'd "headcanon" her to generally ignore genders altogether, but to use "female" (with no other context) more out of convenience than out of a desire to be seen in some way.
Yoursgrub