Rewarding bad behavior, how do we stop?

My MIL lives in a very nice nursing home six miles from us. She was admitted because of a sharp decline in her physical health making it impossible for her to live in a situation where she would not have 24/7 assistance. She has difficulty with short term memory and feeling lonely and bored when she is not involved in activities provided by the nursing home. She lived alone for over 15 years and never had a problem with loneliness or boredom when she was living in her own home. She phones and cries that she is lonely or in prison (her perception) or hasn't been fed all day (not true). My husband has been visiting daily to keep her happy and prevent calls. This evening my SIL left a phone message saying my MIL was upset and crying and could one of us go visit. I was gone from home when she phoned, borrowing a live animal trap because I'd just discovered one of our outdoor cats had gotten in the house and was in my store room (probably having kittens). My husband is at a meeting. I phoned my MIL, who was crying and whining. Told her my husband was gone to a meeting and I was trying to catch a cat. I told her that no one was available to visit this evening. By then she'd stopped whining and said she understood that we couldn't come but she hoped we would visit when we were available. I told her we would visit but it wouldn't be tonight. She said she was feeling lonely and she would just let God take care of her. I told that was a good plan and I was confident she would manage fine. Currently she is getting lots of attention by crying and whining on the phone - during several calls nursing home staff have stepped into her room, asked how she is and she answers in a normal voice that she is fine. Give me suggestions on how you have set limits on manipulative behavior. I'll post if we find kittens.