Other parents with experience with sibling experimentation?

I am a very open minded person so my approach would probably be different than yours but I would say to have a conversation with the 14 year old but don't overreact. She may just be trying to figure herself out at that age.

When you say she was "teaching," what exactly do you mean?
Was she teaching her by explaining it to her or was she actually teaching it by doing it with her?
With explaining, I don't see a problem but IMO, actually being physical may cause problems for both girls in the future.

It's just learning experience. I say good for them and props to your older daughter for being a great sister and teacher to her little sister

sounds very normal to me. have you forgotten your own curiosity and experimenting.

Let’s chat…send me a DM.