Search Results: growing apart

So I've looked around the internet for a bit and I've only seen guys asking if they should send a happy birthday, but not much about girls typical motivations they might feel while in this conundrum.
id love to know the female's perspective on the motivations.

(History)
We've known each other a long time us both growing up in the same church, im 27 she is 22.
We didn't talk much as kids, but 3 years ago i started to get the feeling she was developing a bit of a crush.
She would rub up against me while passing me by seeming to not notice or care that her stomach just grazed my butt.
She would always be around me during public hang outs, she would ask me to walk her to washrooms, she would separate me when looking too happy talking to other girls by acting all cute pulling my arm and saying she needs to go pee. She would randomly bite my shoulder or quickly lick my my leg in public when sitting between them while i was on the my laptop.

We'd text every day for a bit, and the climax was when i got back from a 2 week vacation and we hung out on a couch and she put her head on my lap and we talked for a few hours and i got in her pants and started to play with her ass.

A few weeks later things slowly cooled down, we don't talk much now, but still share the occasional LOOK.
because covid we haven't seen each other in over a year.
This year though i consciously didn't text her on her birthday because the year before she didn't message me on my birthday, petty i know, (our birthdays are 5 months apart).

This year i got one, we haven't really talked for about 2 years. (Don't have fb and don't do bday stuff on ig)

It went as follows.
Her: happy birthday!!
Me: thanks (name) i appreciate the birthday wishes 😁 hope you're doing well.
Her: im doing great anyway enjoy being 27.
Me: I'll try, thank you.
I know nothing special, but the only other girls that messaged me happy bday definitely have a crush on me, so just a bit confused, Girls please help

When I went through school I thought that my friends were for life but apparently not as we have drifted apart over the years... Which has ended up me with no friends or anything close to it

Is it just me or a universal thing?