I agree with Sage and Aggy about the genre limitation with this agent. If she doesn't rep what you're writing now, why bother?
Generally (but not always) when a writer signs a contract with an agent, it's for all works, not just specific areas within one genre, like Aggy mentioned. What if the agent wanted you to turn your YA novels into NA just because it's what she reps? What I would be asking myself is why she wants this MS if she knows your next two will be YA. Or perhaps she doesn't know?
And to add onto what Aggy said, I think it may not serve you well if you do end up with two different agents representing you in such close categories. Think about what might happen if this agent sends the manuscript in question on submission to a round of 12 editors. Meanwhile, your YA agent wants to pitch your YA MS to many of those same 12 or at least the same houses because a lot of them publish YA and NA. But the YA agent would be hamstrung until the NA/adult novel submissions played out. Plus, it might be strange and uncomfortable for the same editors to be pitched the same author for similar work from two different agents who are not at the same agency. That could potentially be an undesirable position for an agent to take on. They have their reputation to think about and all their other authors, too. So they're rightfully cautious about stepping on toes.
Whatever you do is of course your choice, and only you know the full situation, but you really should be thinking of your whole career, not just one book. What do you write now and where are you going as a writer? Aim there. The best idea would be to find one agent who can rep everything you want to write, whether it's on their own or with the help of others at the agency.
I know it's very exciting to have an agent interested in your work, but this is really just an R&R with limitations that don't benefit you. I can understand offering her first right of refusal, but that's a different story than an exclusive.
[And four weeks, in my mind, is a long time for a new agent (who presumably is not overly swamped with clients) to take for revisions when you're on this sort of exclusive. That doesn't even account for the additional weeks or months you'll need to execute the edits.]
Sorry to sound like a downer. Just trying to help you see the potential consequences of how things could play out. Perhaps I'm completely wrong.