That's difficult. I was trying to give her the benefit of the doubt but it doesn't sound like she's doing the caring that she claimed and if that's the case I think you're right that she'll have to pay it back.

Do you know what has actually been happening with regards to the caring? It sounds like she hasn't been caring and you're now trying to think of an excuse for the tribunal that might let her get away with it. What explanation has she given? That aside, lets assume she has been caring and her PIP statement is also true. Is that possible? How far is it between the two homes? Does she drive or walk? She might have great difficulty going out but be able to manage a short distance if she speaks to her mum for "support" before she goes and during the journey if she needs to, or there may be someone at home who provides support before she leaves, or maybe someone gives her a lift. Then she's not actually doing the journey unsupported so it's not contradicting what she said for PIP. What did she put on her PIP form and what did she say in her assessment about her daily routine? If she stated she rarely leaves her home then that's hard to argue, a pretty clear contradiction, unless her mum is coming to her house. If she said she is caring and was honest about that I think that could be valid and not contradict her claim. If she's on her own at home with depression she'd likely be struggling and there could be benefits to her in terms of mutual support if she did spend the day with her mum. The care she provides giving her an opportunity to keep busy, take her mind off her own problems and just have company. Did she have to specify what care she would be giving to her mum when she applied for CA? It would be quite possible for two people with mental health problems to go out and do things together, providing support to each other, even if both would struggle to go out alone. The anxiety may be lessened simply by the other being present. Similarly one with mental health problems and one with physical problems. Has her mum been coming to her house each day? I think this could be valid but it would depend on the condition that the mum has and what care is needed. Is it relevant for CA where the care is provided? I wouldn't have thought so but I know very little about it but assuming it doesn't matter then I think the mutual support argument would apply again. There's no reason to believe her mum is caring for her and no care is returned just because they spend the day at her home rather than her mum's. If all she has been doing is talking on the phone I don't think this would count. I think you just need more information from her about what she has actually been doing and how she has managed to do it despite her difficulties.