How to know whether my crush is really a reserved person or she simply isn't interested in me?

So basically, there is a girl in my office who mostly remain calm, only talks when it is necessary. She is not shy, but i feel like she is introvert, reserved type of person. We both are having mysterious awkward eye contact with each other for few months. One day her friend having farewell party, so I talked to her friend for the first ever time, and smiling and all that. My crush saw this. The very next day of it, whenever me and my crush having eye contacts, she started giving me smile (for the first time). That gave me confidence and I started talking to her for the first ever time, and we started conversation little by little, day by day.

I noticed :

- she looking me already sometimes when i try to see what she doing

- one time when i caught her looking at me, she gave me a smile, then we talked a little in signs (because she was sitting bit far from my seat)

- her friend who got farewell, also started seeing me back then suddenly (looks like she told her something about me)

- later i actually got opportunity to sit right beside her.. from there we actually started talking more than before. She even said me "you are going to like this new seat" with smile

- i noticed that when i sit somewhere near her seat when our known coworkers are near us, she avoid looking at me, but secretly she take a glance on me especially when i am leaving that area.. i have noticed this multiple times

- one time i even felt lingering eye contact towards me when i was saying her something and she was smiling, and i stopped saying, and she continuing looking in my eyes with smile

i feel mixed signals from her side, sometimes feels like she really likes me, especially when we both sit together in that one particular area where there aren't much people nearby, there she talks me nicely and even initiate sometimes... but in another place where there are known coworkers, if we sit there, she hardly even see me.. but take glance of me like when i leave that area or come to that area... looks like she doesn't want to show everyone there that she is looking at me or something

Sometimes she get so busy in her work that she doesn't even look at me

I am just confused whether i am imagining all this or she doesn't like me in that way. Like today i saw her talking to someone on her phone with smile. Maybe her boyfriend? I don't know, but i really wanna know. I have plan to give her a paper with my name and number on it, soon! Is that a good idea? If she is interested, she will text me. Our vacations are going to start, so we can't see each other in office, maybe during vacations, she will message me?