More details than this.
Ask an honest trainer for their opinion, someone that has no investment in what you sell the horse for. COTH will generally give you a good ballpark for a horse if you post more details.
Ask your trainer and also look on the internet for horses that are similar and see what price they are listed at. It can be tricky because a horse is only worth what a buyer is willing to pay and there are SO many factors (age, size, location, temperament, soundness, etc.)
Being realistic, I believe she is worth $1000 or so in this condition, possibly less. However, she is adorable and a good to very good mover, so I feel with correct training she could be worth more. At this point because I know I want to sell her I have to decide to risk putting her in training ($$) and getting a higher sale price for her or cutting my "losses" and sell her as is at the lower price.
15.2, not a kids horse and marish are going to be the biggest obstacles to selling her, IMHO. She would probably need a few successful shows at the local level before you can ask much over $3,000 for her.
Edited to add: Lead change will make a big difference, as will her jumping style. However, 15.2 and marish are big obstacles to overcome.
More info: Starting ulcer meds next week to see if that helps with her marishness. Yes lead change, its pretty easy. She has great form over fences, no she isn't going to knock anyone dead but she is cute and would be very competitive on the flat and over fences at local shows.
I would also say that I really think with some experience she could be a competitive child's show horse. She is super easy to deal with on the ground, the only time she is marish really is when you are in her stall with her untied.