If he likes you then it is you and him and she just has to be jealous
I'm no expert on things like this but I think she'll slit your throat then proceed to decapitate your head😢 I suggest striking down when this person is vulnerable and wounded or using your superior detective skills to show this girls ulterior motives. After all there can be only one God
That might upset her.
If she is your best friend, then that is definitely going to cause a big tension between you to, especially if she told you specifically liked and had a big crush on him. But this is your life, not hers. You can live it as you please.