Girl code....wanting to date my best friends boyfriends brother

Hopefully the title made sense to you all.

Anyway my bff and her boyfriend have been trying to hook me up with his brother and well I did. I ended up liking him and he ended up liking me. Long story short it pissed my best friend off. she pretty much told me never to talk to,him again, lose his number, and that it was just a one night stand. Well ever since that him and I have been texting every day and even plan to hang out this weekend. I wanna tell her but I have a feeling she will flip out again

Any advice?

One more thing I forgot to add...which was weird to me but I guess the little sister of the bf and brother said that I should date the brother and I guess my friend got bugged with that. it is a weird situation I know. That's why idk wtf to do