What does it mean when a girl crosses her arms while she sees you talking to another girl?

[Greateye]

Is this a sign of jealousy?

Why would she lift her chin upwards when she passed by me?

Context:

I've known this girl for a few months, she has placed her hand close to mine while she's showing me something, sometimes looks at me while I'm not looking, sometimes it she looks at me and it seems like she's trying to tell me something with her eyes (it think it's like a gaze). She has placed her hand close to me but she was distracting me with something else on her phone (I noticed this in the background).

She saw me while I was talking to another girl (a nurse), [she was a little far away but was looking at me the entire time, I saw her from the corner of her eye] she has her arms crossed and her body was pointed at me.

While she's doing that she also was looking at me but if I look at her, she would look elsewhere (but then looks back at me when I'm not looking).

A little while later, I see her again, closer (as in, were less than 2 feet apart, Narrow hallway). When I say hi to her she lift her chin up while she says Hi (but barely making direct eye contact).

[Guy13]

A crossing of the arms can mean a couple things. She is blocking out what is being said or the presence of the other person in general. She is likely angry, resentful, and plain old pissed off. It is not a time to push her or talk about something super important. Everything is closed off and she is not hearing you.

[dustybiker]

I’d guess those are. Self defensive and miffed gestures.

[Anonymous]

She might be pissed off at you. Did she have a scowl on her face?

[Akam93]

Maybe a sign of jealousy.