I don't mind you asking! This is new territory for me, as well, as I don't normally do multi-fandom roleplay. I don't know anything about Evangelion. ):

She'd be able to beat it easily, even without knowing about it, with a Master. (A Master is basically a magic/energy source for Servants.) She's quick, has ridiculously high defenses, and has Excalibur. Her Excalibur can level 3x3 city blocks when fully-powered. The problem with that is it draws a lot of energy from her, so ..

Without a Master, it'd be more of a game of dodging/outsmarting, and likely having to withdraw and recover if it went on for too long. She wouldn't want to drain herself dry. If she was desperate, she could throw off a half-charged Excalibur attack and then run for it.

It's hard to compare, really, since Heroic Spirits are so strong in their own canon. I also am not used to having ridiculously strong characters. Should we fight, I would like to discuss results ahead of time and write towards that. I definitely want to be realistic. Especially with her first fight with something like this, she'd be way more cautious and way less likely to want to go all out.

eta: I asked my husband about Evangelion, he knows, and he said she could def beat one with a decent Master.