Melody -
I have a 24 yr o son, divorced with a baby.
I also have a life-long best friend.
If I had told the best friend I had an apartment or even a room - or even an afternoon to spend with her - and then the son *wanted it*, I would have told him, "I'm sorry, it's taken. I told so-and-so she could have it. If you need it, the three of us can sit down and talk it over, but I can't give away something I already gave away, now can I?"
We have that sometimes, I'll make plans to go shopping with my sis or friends and DS wants me to watch the baby. Sorry, but if I have plans already, I cannot.
If I had planned to watch the baby, my friends, shopping, or lunch will have to wait.
If I make a promise, I'm a grown up and I stick with it.
I feel in your words though that your friend feels as big a void in losing you as you feel. And I'd bet she wishes she could do somethiing to fix this mess. She handled the situation poorly, but she'd do it all differently if she had it to do all over again, what do you bet.
In time you might find it in you to write her a letter why this hurt you - easier than talking about it, IMHO - and see if the two of you can put this behind you. Maybe you can resume the friendship, maybe not, but at least bury the hurt.
You had every right to be hurt.