Accidentally took too much equity out of flat

Long story short, my partner and I are buying a flat. She remortgaged her current flat to get some equity for her half of the deposit and turn it in to a buy to let. We are exchanging and completing next week on the new place. Both mortgages all gone through. Lawyer calls yesterday slightly confused as he’s received an extra £200k. It seems my partner took a £270k equity out instead of £70k. I think the broker thought she wanted the max she could get and she did not pay attention. There’s no ulterior motives from her here, just incompetence! I didn’t look at any of her paperwork as that’s her business. She was completely surprised herself and immedietly told me. She just wants to get this money back into the her flat with as few losses as possible. Completely understand this is a ridiculous situation and will likely cost her. Just looking for the best options to explore moving forward as you might have guessed, we’re not the most financially savvy couple, but successful in other ways fortunately!