Most Helpful Girl
The more important question to ask yourself is does her outlook on life and goals for the future work well with your own views? If they do or don't then you can decide for yourself if it's a mistake or a fresh start. It'll be easy to tell once you answer that. Also it will only be a fresh start if you stop comparing her to your ex.
Most Helpful Guy
They're 2 very different people, you need to know that.
Your question screams "I haven't taken enough time for myself, I'm not over my ex yet"
I don't know how long it's been, but comparing a new girl to an ex is a bad, bad sign.