I'm a little taken aback that you specify a sexual relationship rather than a love relationship. Makes it sound like all you want from her is sex. If that's all you are looking for, why destroy a friendship in order to get it?
this is kind of an unusual question because you say that you "feel like you need some sexual realtionship" with them.
If yall are together and decide to have sex... think about your friendship and if it's possible for yall to be just friends with benefits.
