Girl's Behavior

Why does my female friend is shy around me but not when we're in group meetings?

I always liked my female friend. Thing is, she is very outgoing and extrovert with everybody but when I met her alone she acts shy and serious, and kind of more "polite" serving my glass, and things like that. When we are in friend group meetings, she acts as normally as she is but touchy with me. However, I may afraid I could be making her feel bored.
She recently broke up after a long term commited relationship of 6 years. Through the time of her past relationship we used to hang out sometimes with her and her female friends (actually one of her best friends is my female boyfriend). So, in many of those friend group meetings we often ended up hughing. Since last year, we met more often and notice her being more "sweet" with me, more touchy. However, I actually didn´t see her a lot, mainly in those friend group meetings. A couple of months ago she couldn´t attend a meeting I was organizing, and then a few days later invited mi at my boyfriend's place to have some drinks (she was visiting her) and then she told me she was breaked up and she was moving to my boyfriend's place. Since there, we've hang out a couple of times in group friends. Most recently we've been in a friends meeting and ended up hughing after she asked me to dance with her, literally jumped over me and told me "hold me thight", so we ended up kind of drunk and gone in a cab with another female friend. My crush asked me if she could stay at my place but her friend told her that we was really near of her own place. Last time we attended another of those friend group meetings, she asked me to escort her to her place (I live near) but she asked me if I could stay at her place, It was for a couple of hours and actually slep myself on the couch and she at her bedroom. So, why do you think is acting shy and serious with me? Thanks a lot!
Updates
+1 y
I made a mistake. It's my "best friend's place" not my "boyfriends" place. Sorry, hope you guys don´t get confused. Thank you!
Updates
+1 y
Last group meeting, she was talking really loud with a friend of mine and his girlfriend near to me and said that "she didn't had sex since her breakup, that she migh like to find someone, but not any better-than-nothing guy". Funny thing here is that I often talk with my female boyfriend's about the girls I date and she tells me too, but with my crush we never talk about it.
Why does my female friend is shy around me but not when we're in group meetings?
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