u/StatisticianLonely62

I have this girl bsf ive know for years we're extremely close but we've never had like any sexual interactions, but I really wanna have a sexual relationship with her without ruining what we had previously uk? It doesnt even have to be sex per say,maybe like nudes or phone sex, im saying all this to ask whats the best way to approach her in that manner without risking our relationship.