How can I tell she is well trained? Well she has learned how to carry herself and her neck is turned over! Is she a bit lacking in hind quarter muscle? Yes. She IS 20 and probably has not been really used in awhile. Work on her flat work.. work her on trotting up hills.. it will come back.
She has lovely bone, and is well defined throughout. She is a bit roach backed.. but as a horse ages that back can be her friend as it means she is less likely to suffer the sagging of age. This is clearly true and observable here. She has clean legs and lovely low, large clean hocks and low knees. You have quite a nice horse here altogether.
The only thing I do not like is the flash noseband coupled with the Pelham bit and converter. You should never use a flash, dropped or figure 8 nose band with any sort of curb bit or bit with a curb strap or chain. Such a set up is exceedingly harsh.. and as nicely balanced as this mare is in every photo of her being ridden I think you might want to try a snaffle with a flash instead. You can get something with a slow twist if you need a little more control.. as a former jumper I am quite aware she may be very forward. Or you can try the Pelham with a much shorter shank and converter and conventional nose band.
As a beginning rider I also know that sorting out two sets of reins is a bit much.. but a Pelham is much more effective with two sets of reins. From these photos it is clearly the rider is a beginner.. but this horse will really really help you become very good. I wish EVERYONE who wants a horse and needs to learn was this smart.. to get a nicely trained campaigner to learn from.
Thank you for posting this. I hope everyone sees you and this horse!!!
Very nice horse. Let her teach you all she knows.