Why should she receive any payment? No equity was contributed, and hardly anything has been repaid. At the moment, there is 100% financing against the house, zero assets.
Something similar happened to a friend of mine (a long time ago). He bought a house with his partner, and there was still some renovation to do – the relationship ended even before moving in. He then bought her half, paid the property transfer tax on that half again. But I don’t know how the loan was handled.
If she wanted to get out of the loan agreement, the contract would have to be terminated, or why would there be a prepayment penalty?
It’s definitely a really nasty situation, and I’m keeping my fingers crossed that you find a solution.
First, sort out the land register (with the corresponding costs for property transfer tax and notary) and at the bank, keep your feet still for now (you are paying the installments alone) was obviously not an option because she remains jointly liable for servicing the loan.