How do you know if a girl is trying to be FRIENDLY or if there's something more?

I have a friend whose really friendly with everyone, not the flirting type just really friendly and polite and can start a conversation with anyone who talks with her. I recently had the guts to try and be her friend but still have a hard time approaching her because I'm not sure if she wants to be close to me and want to be friends(I'm also a girl) and also because I'm the shy type and socially awkward. I have no problem becoming close to guys however. She would never come talk to me first but I would never approach her either before cause I was shy. Though she talks to a lot of people, she likes to sit alone when shes waiting in line during training. Recently I have noticed her actions change. One hint was that we were at this training center while waiting to play some sports, we were waiting in line and I stood there to wait, she waited next to me but instead of standing next to me, she practically squished herself into me and our arms touched together tightly, but then she got off and we were standing a normal distance away. Now from what I've noticed, she hasn't stood THAT close to someone yet because we all have personal space, normally someone would stand at least 10cm away from another person but she invaded my personal space like it was so natural, and she's never been that close to me before. The closest she's been to me is standing real close to me while I was sitting on a bench. I've met her for about 5 months but see her once a week and didn't used to talk to her for like 3 months. So basically I've only known her for 2-3 months altogether and we would speak for about 30 mins max in a time span of 3 hours every week. So I guess you could say were not close at all since we hardly talk, and I haven't gotten her fb. When we were by ourselves one day, outside the training center, I joked and said I wouldn't be able to see her at training anymore since she said the training days changed and she invited me to go jogging with her to catch up instead which shocked me. We're both training to become more fit apparently and she said we could help each other out. I think that a normal person would answer with "You'll see me occasionally within the week so it's ok" because she will be coming occasionally to training on the day I'm there. However, I was just surprised she invited me to do something outside of training which was out of my expectation since I didn't think we were that close. Then again, she could just be giving me a friendly invite that won't come true. I just want to know if she likes being friends with me or if she likes having me around, because she doesn't initiate talks but does these weird ass actions that confuse me. I like her of course, as a friend but also more than a friend. I've already come to terms with my sexuality as lesbian but I got no clue what her sexual orientation is, and assumed she was straight. She doesn't have a bf I think, and says she's just waiting for the right person and not rushing it. Could someone help me in depicting what actions a girl would do if she was flirting or whatever and what this girl is doing to me? When we stand together I feel somewhat nervous and awkward because shes so close. Like when I said she was sticking onto me, we practically stayed there for a while before someone else came to talk with us. That was the best feeling ever, being so close to her. Any help would be appreciated and sorry this post was so long!