I see an older horse that has been trained for headset rather than proper engagement and carriage of self. Because of her age coupled with how deep/behing the vertical she is being ridde, I would suggest that she needs a good chiro and massage into longing to loosen and then properly build her back muscles. It's an investment for sure and while her price is reasonable, there are going to be additional costs (chiro, massage, and time of retraining at the least) that are certainly a factor.
Conformationally she is nice, movement wise she has been trained to move from the fore, so while I can't fault her for that, I also cannot accurately judge her movement. Her mouth is opened with her jaw braced against the bit showing me a stiff, fixed mover rather than free movement through the back and hind. Does she have potential? I think so. Is she worth the asking price plus the time and energy to retrain an older horse and the investment of chiro/massage to help the muscles remodel properly? That's really your call.
I think you can find nicer for cheaper or the same price that are younger. I'd rather personally take on a greenie than retrain an older horse that has been ridden improperly for an extended amount of time. Along those lines however she does look brave and honest to the jumps which is a plus - and something you may not get with a greenie.
At the end of the day it is really your call for what you are looking for however to me she looks like she needs some noticeable work before she would be considered (in my book) a solid H/J or BN Eventer.