I was glad when she let him go. It's obvious she knows him well, as she says:

I now see it is not in your nature to be content, or confident in love.

She has his character down pat. She knows him much better than he knows her - much better than he even knows himself.

She is a better & more sensible person than he is. She realizes that in his present mind, they could never be happy together and therefore releases him. Her parting shot was superb: