I would say you need some tragedies; they don't have to be severe. The gay girl gets dates and they go badly, she needs a shoulder to cry on and her friend supplies that. I wouldn't turn that into a kiss or anything, just a soft spot for her friend. She needs to build up some sympathy for her friend, and grow to see nothing wrong with her friend's homosexuality (and thus her own, when the time comes).
Love attractions typically consist of three elements in real life. The first two are the basis of non-sexual friendship as well:
1) Similarity attracts. I am friends with people that like the same music, the same movies, the same books, the same games, the same classes. They give us something we mutually enjoy, and enhance the experience. Not only that, but if you and I like the same music, then you can share what you find, I can share what I find, and we are both better off, hearing more of the music we like. That's synergy. And affection is built by shared experiences.
2) Opposites attract. Although similarities are generally necessary, beyond the similarities are ways we are different, in good ways. I'd generally make one good at something the other is not, and vice versa. More synergy; together we can be better at life than the sum of what we can do separately; because suddenly the "team" is good at something I was not good at alone, and vice versa for my friend.
3) Physical sexual attraction. The first two are good ways to form strong friendships, but this is necessary for romantic love.
Fortunately, you have (3) already, the gay girl is physically attracted to the logic girl. Now I'm presuming the logic girl is actually homosexual, not bi or hetero.
So gay girl can fall in love with her friend, and her friend can actually be in love with her but mistake it for platonic love.
But gay girl, after a series of disastrous dates, finally confesses that she thinks she is blowing them up herself, because the dates aren't logic girl. And that is truly who she loves. Her gaydar went haywire, she thought there was a spark there, but if there is no hope, she needs to move on. To break up.
It's too painful to be just friends, and she'll never have a relationship with somebody in love with her if all she ever does is wish they were someone else.
Let the logic girl make the first move. It is the absence of her friend (and the loss of those synergies from (1) and (2)) that makes her review their relationship, and realize she actually IS in love with her. That she isn't attracted to men. So she finds her friend, and tells her that her gaydar wasn't wrong, and kisses her.