The 24 hour engagement.

[Sundae]

Dis - just to say I went through something similar.
Flew over to New York for Christmas, and my BF practically proposed on the plane. Not down on one knee, no ring, just said that when my divorce came through we should tie the knot.

Five days later I dropped him off at his house - we'd had a lousy flight home, we were both shattered and wanted to crash in our separate beds. He said he'd call me when he woke up. A couple of hours after I expected the call I got a text. Saying he was sorry, he was back with his ex girlfriend. Not to contact him as she was coming to pick him up.

Fool that I was, I went along with the silly rules and just moped. I should have screamed and shouted. I should have demanded an explanation. But I should have realised that this was always going to be a pattern with him, and that he had no interest in me as a long term partner, and once he realised he could get away with that sort of behaviour, it was always likely to happen again. And it did. Year after year.

Let her go.
Get closure any way you can - burn your bridges if it works for you.
If she's the right person for you, if she feels you are right for her, it's up to her to come back.

You might have forced her hand with your proposal. But it's shown you something you might have had a hard time realising otherwise.