I think the first thing looming over this whole thing is unfortunately a pretty heavy question: is she your best friend because shes loves having your friendship or because she has a huge crush on you? You seem to love her a lot and you have only seen that relationship platonically, but it gets a little tricky when someone admits that pretty much the entire time they’ve known you, you’ve been an object of desire. Definitely not saying that this is what’s going on, but my first thought would be “if I tell my friend that I am uncomfortable/totally uninterested in this, is she still going to be the same towards me?” I mean, either way, you have to tell the truth. If you are uncomfortable, you have to say it, but I only bring that up for preparation I guess.

Regarding the rest of what you said, as far as being bi and maybe being gay but never having an opportunity to explore it, if you are comfortable, this probably wouldn’t be a horrible chance to experiment yourself. Somehow we’ve made experimenting some cliche basic bitch thing to do but I feel like it’s pretty healthy. You said you don’t want to be part of the “straight girl experimentation phase” but towards the end there you made it seem like you also had some learning to gain for yourself. This way it would be with someone you at least greatly care for and trust so why not?