Why did she make that face when I said I was leaving?

I started my current job last October and 3 day ago I was offer a new position else where. I few after I started like around mid November of last year they hired this new broad that seemed to have a crush on me. I remember she use to giggle whenever I spoke to her whenever we were assigned in the same department.

also whenever the shift is almost over and there is nothing to do my company lets you walk around and socialize with other coworkers or play with your phone. I remember one night this happened and she was talking to other coworkers within 20 feet away from me and as she did I remember she tried to open up to me. she shout it "hey how you doing? are you bored?" to me and left me in a state of shocked.

so after that she became a manager and the confidence I had towards kinda started plummitting because not only is it never a good idea to being in a relationship with your managers but I also though that she was probably gonna look down on me now that she's in a position of authority while I'm still just an assistant.

anyways getting to the point I announce that I was gonna leave the other day and all my managers got sad, they were all together at the moment including her and then I noticed that she got sad and looked away and as she did she started squinching her lips repeatedly. till then I'm not good at reading feelings and emotions that well. can anyone explain why she reacted that way