I don't know what to belive right now..

Ok, somehow I end up posting here everytime I got a problem regarding a relationship and I can't sleep because of it... Even if this time is something dumb.

I have this crush on this girl for the entire highschool, I mean I fell in love with other girls in some periods, but this one, had always a corner in my mind. In the first 2 years of highschool I never talked to her, but this year after I tremendously improved myself in any chapter and somehow detached from the infantile ''total crush'' mentality that broke my hearth twice in the past, so I felt like I could start pursuing her. My strategy was simple, be the best in anything and make her friends be my friends and make them respect me, until she notice me (she is a cute girl pursued by almost every guy in her circle, so a straight forward approach wouldn't work) and surprisingly it gave results. She started a few small talks with me and became very shy in my presence (even if my friends told me that she is anything but shy usually, more like dominant and cold), and I caught her staring at me a few times. I also talked to her a few times via Facebook when I was in a library choosing books and the conversation went smooth as hell, I mean she was asking me stuff about myself and things... It also sent me a picture of one of her drawings.. All good, and now THE PROBLEM:

I am good friend with one of her close friends, a guy, lets call him Tom (in reality have a hell of a name, I'm european btw)... Tom kinda knows that I like her, until now he suggested a lot of times that we would look great together, even if I didn't mentioned that I liked her or even I have the intention to pursue her in any way, he brings her as a topic in our discussions usually.

The thing is that today, my best friends, that is also a older friend of Tom, told me that Tom told him a day ago that me and her don't have a chance together and she actually makes fun of me and the way I dress... I was mind ****ed when I heard that... But my best friend told me that he knows from experience that Tom is a liar and he backstabbed him too some time ago, and from what he knows my crush and what I talked to her (I showed him the Facebook conversation) Tom was lying. But I treated Tom like the best guy, and we were really good friends (or that I tought so) and I see no reason for him to lie and also, why it didn't told me that, and he told my best friend about it?

This thing is messing me up because this days I was planning to talk a little bit more to her or even ask her out... ? But now I'm not so sure about it, and I DON'T want to look like a fool in front of anybody. If this girl don't like me, is ok, I don't mind, I can move on very easily, but I don't want to be an idiot and approach someone that makes fun of me even if she didn't even know me yet (if what he said is true)... I'm pretty sure he is lying but, my question is why would he do that? And also, if he wants to backstabb me he could've told my crush bad things about me or stuff... I actually don't know how to act right now.

Please help me with an wise advice like always :D