You noted a few points that I want you to consider.
All my life I was thinking that I was straight until my second year in college came. I became very attracted to a girl who is actually my closest friend in school.
Could you be attracted to this girl because
she laughs with my corny jokes, looks at me everytime she makes a joke, goes a little but shy when we're together and her eyes got "sparks" everytime she looks at me.
Is she the first person to act this way around you?
You also noted
My suggestions are:
However, it seems like she is not yet ready to date women. I don't know why I was attracted to her.
1. really spend time with yourself to determine if you are a bisexual in the first place since this is a new experience for you or are you saying this because she is expressing she is bisexual.
2. Explore what is making you feel attracted to this girl. Are you attracted to other girls or just this girl?
3. Since you noted she is not yet ready to date women, you have to make the decision whether you are ready to risk the friendship if she does not reciprocate your feelings.
4. She may feel safe around you, so she may be just being herself with you, so be yourself and if it is meant to be let it happen naturally.
5. If you already counted the cost, and ready to go for broke, then Just Do It. i.e. share that you are bisexual and that you like her. The worst thing that could happen is the friendship is over, and the best thing that could happen is you have your first girlfriend.