[@Scarifar] I'd believe so. They're both able to take down a human, I don't see it as much of a stretch that they would be facing each other on decently equal grounds. MG doesn't have training from Asgore though, she's mainly self taught, so she'd be somewhat of a worse fighter, but not hugely. She'd probably be way better at dodging considering she isn't wearing tons of bulky armor. 

EDIT: Also those robo arm upgrades are sure to boost her combat abilities.