Should I tell her now, or wait (LONG read, please at least read)?

Okay well, about the guy she's dating - has she really liked him for a long time before he asked her out? If she hasn't liked him for long and their relationship doesn't seem serious, then that's good. Also, how long have you known her? If you've know her for only a few months, you don't have much to lose by telling her how you feel. Think about it.. if you two were best friends for years and you told her you liked her, she might feel awkward if she didnt feel the same. But if your guys friendship is fairly new, she is less likely to feel awkward. Moreover, do you think she likes you back? As long as you tell her how you feel, it doesn't matter if you wait until they break up or before. Tell her when you feel it's a good time. If telling her tomorrow would make you feel better, then tell her then. Just remember, if she's really a good friend of yours, telling her how you feel should not ruin your friendship. If it did, she's not a good friend. I'm sorry and I hope things get better for you!