How involved does a family need to be with a mother (in-law, grandmother) who steals from us, is eager to start arguments, etc.? We do send holiday cards and call about once a month.
It depends, I suppose, on how much she needs you. If she is entirely independent and is not suffering from any illnesses that might explain her anti-social actions, then limiting yourself to keeping in touch with occasional phone calls might be sufficient. But, if she is ill – which you should try to find out, if possible – then more responsibility toward her exists. In any case, you need not allow her to steal from you or goad you into arguments in order to maintain a connection with her.