Marie Antoinette

If you want to use her make her np on higher level since her NP damage is a bit low.

Marie is more suitable as an Anchor, Stall team member or durable DPS.
Enhancing her NP will make her NP kick harder so the fight will be shorter, she's useful vs males.
Bring her to some Male servant and especially berserkers and casters heavy enemies, she's unkillable there. She's a turtle with regeneration powers.

While Surfer Moe does NP spamming AOE wave clearing and the best at doing her job.
Why not NP 4 Moe on the front, while Marie NP 4 on the back. Using them like this will ensure you gain victory easier and technically almost impossible to lose, also with the help of some supps.

Maybe you can burn the servant that you don't like, from gameplay perspective it's not recommended to do that.
For some F2P getting a Gold servant at NP2, NP3 or even higher is considered blessed by good luck.

Don't waste your luck here, Marie is a good servant and you have her at NP 4.
You can try soloing Beast 2 Tiamat final boss using Marie later, she can steamrolls Tiamat there.
You can reset and replay the stage as long as the battle didn't finish, consider it as a training or a method for trying many kinds of team set ups.
I don't like to give people spoilers and don't mean to, you have both servant that can finish harder content with no real difficulty even if the challenge for some people is really hard.