Interesting, I actually really like her, I bet she will be a blast, but for dressage??
Well, who really knows until you try her, so go ride, if she has been for sale for a long time they may be negotiable.
She is fighting the bit, gaping and getting behind the bit, I'm guessing that being asked to do pleasure is anything but pleasurable for this one.
There is a lot of work to be done, probably just chilling and making her a trail horse for a while, letting her go forward and start reaching into her strides again, and then bring her back into training.
Something about her says she is like my Ace, fine to do it, but sometimes quicker than you wanted,
. Like Ace though she does look like she is trying to please, so to me if your aim is to be a higher level successful dressage rider, pass. If like me you really enjoy working with a little bit of a challenge and your reward is doing modestly well in lower levels, then why not.