My gf once said she wanted to try new things sexually.
I tried the checklist that someone mentioned in this thread once. I even edited out some of the fetishes I thought might really freak her out, but left the diaper-related ones in amongst some fairly mainstream things like spanking and whatnot.
She said they were all weird and didn't mean new things like that.
But eventually it turned out she did like a little spanking amongst other things (including a little bit of AB stuff) and some of her reaction was just... upbringing or something.
Don't let the issue just die with one try. Sometimes people just aren't ready to accept something like this right away, but eventually might even enjoy it themselves, when they get to really think about it.