Sister (allegedly) use my electric razor as a dildo.

My sister (17f) is visiting and asked to borrow my electric razor. Of course I (14f) said yes because we share literally everything. When she put it back on the charger in the bathroom a few days later, I left it be and went to use it today. When I took it off the charger (it's one of those chargers where it's a block that goes in an outlet with these stick looking things on top that insert into the razor), I few crusty things that looked burnt came off from the bottom of the handle part of the razor. I immediately got suspicious because when I looked there was crusties on there that looked clear and a little brown, dried to the shape of the inside of the razor where you insert the charger block. I went to her room with the razor and asked her why it was there, and she simply said she didn't know. She was super defensive about it and gave me a bunch of attitude, which made me even more suspicious. I believe, based off the fact she didn't return it for a few days, the color of the crusties and how they dried (suggests they were a liquid or liquid like substance at first), and his defensive she got, that she may have used the handle of it like a dildo. I'm not sure how to approach the situation since I don't want to embarrass her and am a bit embarrassed myself, and I know for fact she's just gonna get defensive and start an unnecessary argument. How do I approach this?