Right at the start of covid, I started a somewhat niche hobby and became friends with this other woman I met on a forum for said hobby. At the time, I was stuck in the middle of nowhere so spent a disproportionate time online talking to her.
About a year later, I came back home and we decided to meet up as she was ~30 mins or so from me. All went well and we started meeting more and more frequently. We both like women and there was always quite a bit of flirtation but we never really took it any further.
8+ months later I started trying to distance myself from her because she was very intense and I couldn't deal with how rigid her thinking was or how she seems to pride herself on how good she is at 'doing research' on anyone (usually family or friends) online. Our contact got more and more infrequent until it stopped. I don't have any form of social media whatsoever so aside from WhatsApp there was no way she could contact me/see what's going on with my life.
After that, once every few months I'd get a message from her with random things like a picture of a kombucha bottle saying "isn't this the brand you used to drink" or Taylor Swift concert dates saying "bet you're going to this concert" etc. I blocked her number once and she messaged my friend asking if I was doing ok! I've never ever given her my friends' number and they've never even met!
Last year I graduated after having gone back to uni in my late-20s and I received a message from her not 15 minutes after the congratulations message was posted by the school with the list of graduates asking me why I switched courses. I never once told her I was going back to uni! Yesterday, same deal. Received a message from her saying "oh you're working at X now?". Apparently she found my work email that contains my very unique name on the web.
What can I do about this? She hasn't done anything technically wrong but it's creeping me out. I don't want to change my number as I've had it for almost my whole life and I have too much linked to it by now.