Ex adding more to joint mortgage

monty-doggy

I’m stuck on a mortgage with my ex.
(children live there)
she’s living there with her husband so I no longer pay towards the mortgage.
they’ve changed it to interest only and have not paid it in over 12 months. (And prior to that there was periods they didn’t pay too)

she’s trying to consolidate the arrears onto the end of the mortgage which increases the debt and the term of the mortgage for me too as my name is on it.

can she do this if I object? 

Thanks 

lonibra

in reality you can do everything online without the other person knowing but in theory as a joint applicant it will need your approval.