It is natural for you to feel that way towards the girl you've developed a soft spot for. However, you becoming obsessed with her, maybe is as a result of the time you've spent with her coupled with you finding out that both of you have a lot in common. Presumably, all these things has made you to be in love with her without you knowing.
You see, love is something we have absolutely no control over. We often find ourselves in its embrace without even realizing we've been taken. And we might think, it our minds playing tricks on us. And sometimes, we feel we can fight it with our own will, until we figure out that it's not something we can easily rid ourselves of from. This manifests when we deliberately attempt to end the love affair, and with time, we'll then discover that it wasn't what we thought it was.
As for your case, find a way to speak to her again, and pour out your heart on how you truely feel about her. You can't predict, she might just reciprocate the kind gesture. Good luck!