I don't know what to do

So today my best friend said that she wants to be Ina relationship with me, and she will leave her boyfriend (they have been together for like 3 years) for me. But the thing it I don't know if I still have feelings like that towards her.

I also don't want her to leave her boyfriend because of me, as it will make me feel very guilty and uncomfortable.

I really don't know what to do about it. I would really love some advice.