Is She Into Me Or Not?

I am a 30 years old guy and I met a 20 years old girl in a spanish class about 2 months ago. I get some mixed signals so I wanted to ask for your opinion.

First of all when it happens to be alone with her (waiting for the lessons to start) she is quite talkative with me asking questions and keeping the conversation going, h0wever when there is another person in the room she is quite quit and gives one word replies eventhough generally she doesn't seem to be shy.

There are times that I feel that she is totally into me and other times the opposite, for example one day there was a public transportation strike in my city and I offered to take her and a few others with my car to their home (our homes are in the same direction) and she refused by just saying that she will find a way. I figured out that her dad came to take her but she didn't mention it as the reason (I felt like she didn't want to get to my car)

By the way this same day she had come with a friend of hers who wanted to ask about starting lessons and while we were only the 3 of us there was no talk (not even with her friend) but when her friend got out to take a phone or something like that, she was again talkative to me.

There is another thing, there is another guy in the class about her age with whom she almost always go to the same direction when we are leaving. Their homes are in the same direction but a few times they go to the same direction eventhough they don't go to the bus stop. One time I found them together in the street (after the class we just took different directions but we met incidentally a few minutes later). She looked upset and without even asking her she mentioned immediately that she was going somewhere neutral. The next time we had class, they came together (this has happened only 1-2times) and again without anyone asking she immediately mentioned that they were just met outside the building.

Occasionally she seems quite friendly with this guy (laughs to things he says, looks at him etc) but she started doing that only the last 1-2weeks and when I saw them sometimes from afar in the bus they weren't talkative or showing any sights of indimacy while being together.

Lastly this guy was friendly with me in the beginning but now he rarely talks to me or just gives one word answers and in a not so friendly way.

So to summit up, generally I would had already asked her for a date but flirting with her in front of someone who might be her boyfriend or have feelings is not my thing, let me know what do you think?

P.S: All the other students in the class know each other for about 1 year so I am the only one who got to this class 2 months ago