Check out the answer you got last time you posted this question:
What's going to happen to you? Maybe nothing.
But if you didn't sterilize the vibratror or cover it with a condom, then you could get an STD or yeast or bacterial infection if your mom is carrying one.
And you also need to be honest with her - otherwise next time she uses it, she'll be unknowingly using a vibrator with your bodily fluids on it. That's really not a nice or fair thing to do to her.
I know it's potentially embarrassing for both of you, but since she has a vibrator, I'm guessing she may be pretty open to talking about sex with you.
Maybe she'll have some ideas of ways in which you can satisfy your curiosity without borrowing other people's sex toys.