Well I have read that you have passed on the horse, but I'm going to chime in anyway!
(because honestly, I probably would not have passed on her)
She came up with grade one lameness in her front left, and when the vet did a flexion on her left hind, that increased her front left to grade 2 for five steps. He proceeded to do an X-ray on the front left, he said she has some minor oa in her coffin bone. He said he thinks she might just need some cortisone injections every 6months to a year.
Grade one doesn't concern me a whole lot. As reference, my Shotgun almost always flexes off on his front right foot. Back when he was 4, he had a minor strain of a tendon that has since completely resolved and gives him no problems .... yet he ALWAYS flexes a bit off on that foot. He's 9 this year. Sometimes, horses might flex off but it may or may not be a problem.
Yes, I get that the horse has some bony changes in the coffin bone but that's isn't a big deciding factor either. My horse Red has no
changes on x-rays but he still has heel pain I've been fighting with for the past 7 years (although he's doing awesome this year!) And my horse Dexter does
have changes on the x-rays on his front feet, but they don't really seem to bother him too much.
What would be more important for me, if I were looking to buy, is how does the horse move and ride?
Did she exhibit any signs of lameness at all or any problems at all? If not, I would place less weight on the PPE results if the horse was an absolute perfect fit otherwise. For an assumed 12-year-old horse, I feel it going to be pretty rare that you find one with no lameness problems whatsoever. Something will always be found on a PPE. Always.
Maybe I am used to dealing with lameness, having performance horses that get ridden hard, but what you describe would not automatically cause me to pass on the horse. I'm not afraid to inject/shoe/supplement a horse if they need it.
However, YOU have to decide what YOUR comfort level is. If you are not comfortable managing something like this, then you are correct to pass on her.
And of course, always make sure your decisions are made with your head, and not with your heart (because let's face it, they are ALL easy to fall in love with!!). So if she really, truly, is the right fit for you and what you are looking for, and you aren't afraid to manage what she has with your vet's help, then go for it. If you'll be able to find another horse that fits you and is what you are looking for (without this type of issue), then keep on looking.