Friend ghosting

I've recently been ghosted by a good friend. I get the memo that she doesn't want us to talk to each other anymore but I can't really figure out why and what to do.

Here's the backstory:
I've gotten close to a female co-worker while we were working on a same project - we are the same project but completely different sub-team, we report to two different supervisors, so we do not exactly see each other on daily basis but occasionally. Both of us hit it off really well as we genuinely like talking to each other. We also whats-app each other off-work occasionally but she isn't great in online presence but not complete disappearing act. During firm events and group lunches, we would just talk to each other a lot as well.
Probably due to us being close, some colleagues started rumors - it got awkward because I am in a relationship (everybody in the team know this) - and the rumors morph into us sneaking around and going on dates (which we never did). I discussed these rumors with her and she said "we did not do anything wrong" and I made it clear as well that we are good friends and it would be a waste if these rumors ruin our friendship. Still, after some time, she started ignoring me and I got her memo. I started to distant myself away from her too. Eventually, I confronted the person who started the rumors and he apologized to me and to her.

Weeks went by and there was a dinner event. I bumped into her at the entrance and as I was about to enter, she asked me to step outside to talk. We didn't talk about the rumors or how we stopped talking to each other, we just chat about everything else the entire night. I guess that is her way of telling me she didn't mind the rumors and wanted things back to normal.

Since then, I could tell we were getting closer as we started to hang out outside of work - always in a group but she would just chat with me. I would tell her to talk to others but she is the kind of prefers to stick to a friend who makes her feel comfortable.

After our project ended, it meant we would see each other a lot less. But we did hang out during lunch and we would take occasional walks for coffee. Not long after, I was assigned out of state for about 1 week. And during the week, she whats-app me constantly, a lot more than the usual (as I mentioned, her online presence isn't great), which made me glad as I think we were becoming much closer friends. And when the week ended, she completely ghosted me for weeks. I felt odd because she was all warm and friendly online before, and without warning, she completely ignored me even when I initiate conversation online.

I somehow bumped into her at work and passed her the souvenirs I bought when I was out of state. She seems happy to see me, but I didn't ask why she ghosted me. I did sort of ask why later on whats-app (and she was replying at this point), she just said that is how her personality - but I know it isn't to the point of ghosting for weeks. I didn't pursue further because I get the memo - she doesn't really want us to contact each other anymore...but I don't really understand the sudden change. Is just I really like our friendship and it is quite a shame for it to end up this way.