Maid: Someone who repairs and maintains their aspect (edited from keeping aspect under control). It’s also a pun, as they are metaphorically (maybe literally for some aspects?) made of their aspect, which lets them lend their aspect to others when they need help. 

Doom: Fate (specifically an unfortunate fate), futility, misfortune in general, sacrifice, and death. Time has an association with death, but doom directly deals with it. It heavily involves ghosts and the afterlife. This aspect seems to be connected with rules and restrictions. It's usually tied to the specific event(s) in their sburb session that will doom everyone.

A Maid of Doom is someone who orchestrates doom, thereby maintaining it. Their actions lead to causing misfortune. This would likely start out as something they don't really have much control over, unintentionally screwing things up for themselves and their friends. They'd sort've behave as a bad luck charm, doing things or ending up in situations that unintentionally start a series of dominoes to fall that lead to something bad happening. However, this doesn't necessarily have to involve causing bad events for themselves and their friends; if you wanted to be kind to your Maid of Doom character they could just have a knack for screwing things up for their adversaries in the same way, and it could absolutely be something they intentionally do.

As they grow more powerful, they would develop an innate ability to know how to cause someones death in more ways than just killing them outright. They could also have a powerful intuition when it comes to knowing how to screw someone over generally.

A more abstract thing that comes to mind is that since doom is directly related to death itself, a Maid of Doom might be able to maintain the afterlife and death. In Homestuck, the dream bubbles only exist because of Feferi, a Witch of Life who broke the rules of death for characters all across paradox space by working with (begging) the horrorterrors to create them, meaning they're not something that naturally occur within the Homestuck universe. So, if you wanted dream bubbles to exist in your own story, I think an incredibly powerful Maid of Doom would happen to find a way to create them, perhaps through the same method Feferi did.

They would not be able to revive anyone in spite of the technical interpretation you could make with a Maid of Doom being someone that repairs death. They themselves are made of death. They supply it. They maintain it. Repairing doom would be them fixing a plan to bring the downfall to the black king or another adversary if something happens to mess that plan up. Them having the power to revive others wouldn't fit narratively, as it would make them a life player. A Thief of Doom can only revive someone at the cost of death themselves, because that still like, thematically fits the aspect? Not sure how to word it properly but I hope my point gets across.