I don't know what to do in this situation and it’s frustrating me?

So there’s this girl I like at my job. Last Wednesday we talked basically the entire shift and it increased my feelings for her. But my friend likes her or well he liked her. She rejected him like a couple days ago. He still talks to her like before and nothing really is different. Like part of me says do what you think you want which is to date her. But another part is to be a good friend and not date a girl he got rejected by. Now I’ve literally never been in a situation like this so before asking my friend anything I want to see what people on here would do
I don't know what to do in this situation and it’s frustrating me?
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