My mom is gonna take me to Fanime since I'm under 18 and it's my first convention. I already pre registered. So does she need her own badge to take me?
Here's some information you'll want to consider first. Do you have a form of government ID to use to pick up your badge (driver's license, state ID, passport)? If not, she will have to accompany you in line and present her ID along with your school ID to get the membership since that's the only way they will accept school IDs (as far as I know). If you have a government ID though, don't worry. You can present that and you'll be fine.
Now to clarify, is she just dropping you off, or is she going into the convention with you? If she's going with you, then yes, she will need her own membership/badge. Since you're already pre-registered, I'd highly suggest you register her as well if she is going. That way you won't be in different lines and she won't have to wait longer to get her membership since pre-registration and early registration has a different line than at-con registration. Don't worry though, the lines will be clearly marked so you'll know where to go.