Sounds like you're caught between the proverbial rock and a hard place!

If you do tell her, don't use the word "hate" but maybe just say that you don't think she's his type. A small stretch of the truth to save her dignity wouldn't hurt. I don't think I'd offer the information that he likes you when you do this, though.

If you discourage her from asking him she may find out that he likes you and may think you intentionally discouraged her because you want him for yourself. You don't say that you do, but she might look at it that way. If you tell her, don't start a romantic relationship with him if you value the friendship, not at least until she's become fascinated with someone else.

If you let her ask him, then she's probably going to be hurt and disappointed when he says no. But it sounds like she's going to be hurt either way. If you're friend is an honest person and can take bad news well, you may as well save her the embarassment of being turned down by him, if you're certain that's what will happen.

I'd hint her in the form of personal opinion, let her do what she wants and step back to the see the result. In the end of the day, anything's possibly really.

This is quite complicated need to know her nature and intimacy between you too what ever u do think a lot .
Best of all i would remain silent. and watch for the right opportunity

I have been in this situation before and trust me you need to tell your friend. If you keep this from your friend and she finds out that you knew about it all along, then this could ruin everything you and her have together. Whatever you do, PLEASE don't talk to her boyfriend. That would be wrong and could lead to some serious consequences. Just go up to your friend and tell her the truth and if she was truly your friend then she would understand and there would be no conflict. For the boy you need to tell him that you have no feelings whatsoever for him and he talks to your friend, so you can't treat her like that. Tell him to leave you alone!