Just be honest with her pero wag mo agad i-pressure. Sabihin mo na fantasy mo lang siya and okay lang sayo kahit hindi siya comfortable. If she really loves you, at least she’ll hear you out and pag-usapan niyo nang maayos
Personally, I’d choose FUBU because it feels more casual and less rushed.
It can be better if both people are comfortable and have clear boundaries.
But if both only want something casual, ONS can also work as long as there’s mutual consent.