My friend let me down because of rain

I have a long standing friend who I have had a very close relationship with for many years. She lives a few miles from me, she is single, lives alone but goes out singing at least twice a week. She refuses to use the telephone and expects people to contact her via email, she also doesn't like people visiting her, although she has a lovely home. Until last November when she broke her hip we met up quite often or she would come to my house, if she has a problem she will use the phone and my husband and I will do all we can to help her. I've only seen her about four times over the last 12 months, apart from visiting her in hospital - her choice. When we do meet it's just like old times.
Last Friday we were supposed to be meeting at 2pm. At 1pm she said that she didn't want to go out because it was raining! Her car is parked just outside her front door and the place we were meeting at is a very short walk from the car park. Am I being unreasonable to be very disappointed and maybe even a little angry at being let down for such a weak reason? She is younger than me and fully recovered from her hip replacement. I have put a lot of effort into this friendship but I am wondering if it has run its distance. About cancelling she said 'is this alright?' I replied 'if you don't want to come out it has to be, let me know when you are free'. I feel a bit bad about my attitude - but should I?