<human>: Can you provide a brief rundown of the text in within 3 sentences?

I have known my friend for about 7 years, and his sister recently told me she has had a crush on me for a long time, about 5 years. 

I talk to her often, and she has had conversations with her brother about me and her, since he knows she has feelings for me.

He told her doesn't mind if we date, but I'm not sure if going ahead will still start issues between him and I.

Also, my schools prom is coming up in about 2 months, and I'm not sure I'm prepared to take her to it because only my grade is allowed to go alone (Junior Prom-Juniors only). 

I don't want to hurt my friend by dating her/taking her to prom but I do want something with her.

What do I do? Give up on her? Date her and possibly take her to prom? Wait until a better/ more convenient time to start something? Any advice will be appreciated. Thanks
<bot>: longtime friends sister has feelings for me, I like her too, but am not sure how to move forward even though said friend is supposedly OK with us dating