My crush laid her head on my shoulder - does it mean anything?

Hello everyone,

One month ago, I've moved from my home town to another city to study, and there I met an amazing girl. She is pleasure for both eyes and ears. She is smart and kind and we have so much in common I find it hard to believe she's actually real. After knowing her for some 3 weeks and spending time with her (in company of our other friends, rarely alone), I've found out she has a boyfriend. They've been together for some 1 year. That night, once I was alone, I cried. I'm 19 and I haven't cried in years (just so you can guess how much it hurt me). I'm crazy about her and it's obvious she likes me too, but not in the way I like her, since she already has a boyfriend.

A week ago, we both left the city where we study to go to our homes for the weekend; she went to her hometown, I went to mine. Afterwards, we took the bus together to get back to college, and on the bus station, boyfriend came to escort her. Once they separated and we entered the bus, she has teary eyes. She wasn't exactly crying, more like quiet sobbing. She was like that for some half hour, and I really tried to light her up as much as I could. We listened to music together and joked, and after a while she seemed a bit better. After a while she got tired and tried to fall asleep, but couldn't really get comfortable. Then, out of the sudden, she placed her head on my shoulder.

Now, I know it's not THAT much of a big deal coming from a girl that knows you. I've had my cousins, sister, and a couple of girls from my class in high school rest their heads on my shoulder, but I've known them for YEARS, while this girl I've known for 3 weeks. I felt like a god, with her lying her head against me. I'm sure she didn't do it by accident: she was awake when she placed her head on my shoulder. I know that because she was changing a song on her phone at that time. She lay like that for some 10-15 minutes and then got her head up. For some 10 minutes we didn't say a word to each other, and then she said something like "This is the first time in my life that I've managed to fall asleep on a bus."

So right now I'm really confused. The girl I'm madly in love with is not single, but she does enjoy my company, plus the whole sleeping-on-shoulder thing. I just want to hear the opinion of girls on the forum: does her placing her head on my shoulder have a real meaning?

Thank you for reading this, I know it's really long.

TL;DR
The girl I met 1 month ago and am madly in love with has a boyfriend. When I was with her on the bus, she wanted to sleep a bit and placed her head on my shoulder for some 10 minutes. Does that mean anything more than just her being tired?