Yeah man these people saying "definitely no interest" are wrong. It seems like interest, but it's certainly possible that there's none.
I got some very simple advice: just ask her out. It might not be the "perfect" advice, because some women don't like to be asked out directly, liking keeping it ambiguous or whatever, but I personally would be annoyed by that. If the other person disagrees to a simple dinner or walk on the park or whatever, then obviously the interest is not large enough or there are some other issues I wouldn't like to deal with.