Landlady doesn't "allow" rent allowance because property isn't split

Ok so I've been renting this place with my gf (we are in a separate house within the bigger property, we have separate street access and fulfill all requirements for rental allowance).

Since the property isn't split (there's only one street number), the landlady says we can't apply for rental allowance because that will incur in extra costs for her to split the property.

This is clearly in a legal gray area since we fulfill all requirements, and now she is refusing to give us the necessary information to apply for the rent allowance.

Is there any way for us to have some sort of legal support in requesting this allowance? I'd hate to lose the place but I don't see much alternative, me and my gf are losing around 800€ a month by not having allowance :/