Yah, friend may not *know* she's crossing a line unless you tell her. In her world, that may be what friends do, is share showing of toys. I had a roommate once, she was so excited when she got her new whip and wanted to show us all. She wanted to show how lovely, and I allowed her to lightly swat my calf (cat o nine tails). The next day I had bruises and she was completely jealous (me=easy bruiser, her=not so much). So not my flavor. So not the level of intimacy in my relationship with her, she was a roommate, not even a friend (friendly, yes). But it's not a line for me, and I didn't mind. She wasn't trying to persuade me to kink, she was just excited about her stuff.
In my experience, lots of women do that; we start in childhood. 'Wanna be friends?' 'Sure' 'Come over after school' *proceed to show toys. As adults, sometimes the toys get very different, but the pattern is the same.
So, I agree with gg, no need to lose a friend because we take care of ourselves. 'I'm glad you have a hobby/pasttime/kink/whatever, but I'm not really into that. Could we go to the kitchen and have cookies instead?'
Love is that condition in which the happiness of another person is essential to your own...
Robert A. Heinlein
Me: female, bi, (formerly hinge of a vee)
with FirstBoyFriend (FBF)(moderately long-distance)
and no longer with CurrentBoyFriend (CBF)(who now lives in a house far away-with stairs I can't climb)