Mortgage lender thinks I'm renting?

Ok so my parents own two houses, they live in one and my husband and i moved into the other one 2 years ago. We were paying the cost of the mortgage to my parents and they would pay the mortgage.

My dad died over xmas last year so to lighten the load on my mum we decided to pay the mortgage direct from our account.

Now the mortgage company has seen this change and thinks she is letting it to us. What do you think she should do? They are saying she needs to move back in. But many people have more than one family home? Should she just say she has moved back in? Help?!

P.s. She lives 5 mins away from me.

Thanks all in advance. X

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