Toxic friendship?

I would like to ask what people think about my situation with someone whom I had considered to be a good friend.  We've known each other for over 20 years, and worked together as MTs for a number of years.  We've been to each other's homes for dinner and have done things together socially over the years.  She's been a good friend to me, and helped me a lot when I was recovering from surgery on my ankle, for which she's been properly thanked many times.  She's married, I am not, her children are grown and gone.  What has me feeling bad and questioning the friendship is that whenever I phone to ask her to do something such as go out for lunch or breakfast on a day off, she tells me that she has to consult her "schedule," won't give me an answer, but tells me to call back.  Many times, they just don't answer the phone, and her husband has picked it up and hung up on me on one occasion.  This past week, I was told to call on Sunday for a decision about getting together, but never to call at 5:00 because that's their dinnertime.  When I did call this week, I got the answering machine and she did call me back, but instead of asking me what I wanted to do, told me that we would go to a certain restaurant for breakfast, what day and what time.  I asked if she could pick me up as she drives right past my house, but that was not possible because she needed to get groceries after breakfast.  I have a car but just thought it would be easier to go in one.  Needless to say, I got upset and we are not going to be doing anything.  This example is the way it usually works.  She doesn't read my e-mail, and never calls me, I'm always the one to initiate any social get together.  She's retired and involved in a lot of outside activities, but my goodness it's a sad world when we can't make time for our friends.  I'm feeling very manipulated and I'm sure this "friendship" has reached an end as I placed the ball in her court by telling her to call me when she wants to do something, which will probably be never.  It's sad, and I feel guilty when all I am doing is standing up for myself.

If anyone has been in a similar situation or just wants to share, feel free, I'd appreciate hearing your thoughts, and please no snarkiness, it's not what I need now.