Why did she block my number? - 1

So I found out that this girl had blocked my number on iPhone. I can't call or text her. I always thought that you blocked someone when they were harassing you or just not leaving you alone. Since we had this fight I barely have contacted her. And now I realized I've been blocked for months? Why would a girl do that? Does it mean that she cares about me and doesn't want me contacting her to stir up feelings?

Also it's weird because I unblocked her and friended her on this other messaging app, and after a couple of days she accepted. This was about a month ago. I haven't sent her anything yet. I don't know what to do?

Ps she thought that I lied to her about having a girlfriend. I was on a break with my girlfriend and then had sex with this girl. I thought we liked each other a lot and that would be enough…
I don't know what to do?

Added (1). To be clear, she told me before explicitly to never expect anything from her… So I didn't and we had sex and then she freaked the hell out. I thought it was pretty intimate btw