[E-Revonut]

MMM combo is most likely your best bet and best bang for the buck! It'll push that truck without a problem on 4-6s but for best run time no matter what batteries gear it down if she's not concerned with speed as much. 4s is more ideal for it but it can be safely ran on 6s, it'll just be a missile! If speed isn't a concern gear it for low 30's and she should get plenty of run time with a decent set of lipos.

P.S. Congrats on getting your fiance into the hobby, if she enjoys it she'll understand it when you spend all your wedding money on it! LOL