Whether you want to use the label “narcissist” or not it’s pretty clear this person is awfully abusive. It’s not just that she insults you and berates you, it’s the control and the chipping away at any sense of stability and self-confidence. Her behavior is very clearly “financial abuse”—but how can money be used to abuse? Control, control, control. $6 for a memory card becomes a lever to control you with and you are right, it cuts you off electronically, and no, you are not overreacting, it’s a rotten thing to have to put up with.
It took me a year and a half to escape physically and another year and a half to escape legally. It helped to think about my allies in life—and I did a lot of reading and posting here to help me put up with the daily onslaught.