That's a very good and clear response. You've not cut her out of your life, or burned any bridges as far as I can see but you have explained to her (again) why it has upset you.
I have experience with a falling out over a wedding - my best friend announced she was getting married when I had just found out I was pregnant.
She asked me to be a bridesmaid and I said I didn't know if I could - I mean I'd love to but I was going to have a very young baby and it was my first, and neither of us knew what to expect.
Also we lived a really long way away and it would mean travelling, and I wasn't with the father properly so wouldn't have any help, I knew he wouldn't want to come.
So I kept trying to say, I probably can't do it, but went along with the planning as well, helping decide on dresses, finding some in our branch of the shop, and so on, even though I didn't think I'd be able to go. I kept on saying I don't think I can, she kept saying 'well do your best and please try to' and it went on, wavering between yes and no for months.
The nearer it got the more convinced I became that I couldn't make it and the harder I tried to tell her this but the harder she tried to persuade me, and didn't seem to be able to understand.
In the end, it was a disaster, as though we'd decided I wouldn't be a bridesmaid, I was still invited, and it finished up with me trying to say no right up till the last minute, and her only realising I meant it a few days before the wedding. She was very, very hurt, I had an 8 week old baby and was all over the place, she said she cried because she didn't want to get married without me there
which I didn't understand at all, at the time - I didn't get how I mattered so much.
She wrote a lot of letters, alternately angry and sad and kind and cross - I didn't write anything - and then about a year later she wrote saying she was pregnant, and I called her and we got slowly back on track.
It was a huge, huge misunderstanding and she felt I'd done everything wrong but I'd been like a rabbit in the headlights, and yes I'd got it wrong, but I hadn't meant to. I was just a thicko with a baby on the way and very little support.
Thank God we did stay friends then - she went on to have another baby, I had another, we were very close for a few more years and then, suddenly, when she was in her early 30s she died.
I still think back to the wedding fiasco (she had a brilliant wedding, a lovely husband, millions of friends) and feel sorry for not being there. She was very gracious.
I hope you two do stay friends and somehow get through this blip.