Had it happen to me with what I thought was a close friend. The first time, we were supposed to go on holiday for 2 weeks. The day we were leaving, she told me that she could only go for a week because she'd met someone special.
Needless to say, I'd stumped up the payment for the holiday already. When I got back, she'd moved and I heard nothing from her for years, until a mutual aquintence got in touch and told me that she was in desperate straits and needed me.
Stupidly, I immediately put the past away and went to her. She had been accused of assaulting her baby, who was then in GOS childrens hosp. After they went home, I visited a few times but whenever I arrived the man would leave and sit in his car until I went home. After a few weeks, I told her that he made me feel very uncomfortable and she had my address, should she need me. Nothing for years and then she turned up unannounced at my birthday dinner.
She was younger than me and had made new friends so I left the runing to her and it slowly devolved to visits on Christmas and birthdays only, which was fine by me, but a few years later, it started again. Telephone messages went unanswered, cards and letters ignored and emails not answered.
This time, I've had enough. Regardless of her need, I would not have anything to do with her ever again. I could not do this to anyone I considered a friend and don't understand how anyone can do it to anyone else.
It is diabolically rude and hurtful.