She's not a moron so she won't do anything that will kill the project, but it is under her authority, and I wouldn't be surprised if she had a lot to say about how the project should work and what goals it should have. I also wouldn't be surprised if she made us offers we couldn't refuse regarding it's direction.
The project is not under her authority, the location is, that's the point I was making, there's only so far she can go before Mathilde can just say. "Well I'm off to work with Kislev, have a good one!" and Mathilde loses a lot less than she does in that scenario. That's why I called Mathilde the stronger partner. Obviously like you said she's not an idiot that's going to tank her credibility by chasing off an enterprise she invested a good bit of her legitimacy into, and neither is Mathilde interested in wasting time and goodwill doing that unnecessarily, so they'll both work to find accommodation with each-other, but the matter of where the leverage lies still exists.