I'm going to add my two cents-she is what you are looking for, you like her, buy her.
Teaching her to neck rein and move off your leg should be an easy fix. I bought my mare in September-she didn't neck rein. Now she does. She's not perfect and she will never be a reining prospect, but she steers well enough for my purposes-trail riding- and that is what matters to me.
My mare is a TWH. No one else at my barn rides a gaited horse. We do just fine on the trail. If we get too far ahead I stop and wait, or we turn around and head back. no big deal.
again-a calm minded, well trained horse is hard to find. I think you will be sorry if you miss this chance.
good luck whatever you decide.