how do you bring up a "no" without sounding harsh or like youre rejecting her ideas

shes been suggesting we try a thing with another woman alone (no men) and... im just not into it. but every time she brings it up im like "yeah maybe" cos i dont wanna make her feel rejected or like her fantasies arent welcome. its been 3 months of "yeah maybe" now and i think shes catching on that its actually a no. how do you say no to a specific thing without making your partner feel like their desires arent safe to share? im worried if i say a hard no shell stop bringing fantasies up at all and thatd be worse for us in the long run...

obuny obuny

obuny — online community for consenting adults

obuny is an adult community and chat platform for couples and singles. Encrypted private messaging, public rooms, anonymous Q&A. Free, beta. Available in French, Hebrew, English, German, Spanish, Italian, Dutch, Portuguese, Russian.