As long as one is living apart, the bank cannot calculate the figures/income. It may be that she has to pay quite a bit to the ex each month – who knows. The bank does not know.
The ex has a right of first refusal if he is currently listed in the land register.
the opposing party is somewhat problematic.
Is it currently also his house?
It can also be something like Russian roulette, financially investing in her house without being listed in the land register oneself.