What to do now? PLEASE HELP!

Okay so I rescues this starved little filly, and I would like to know how old she looks to be in the pics I send, my other horse Paloma is in the pics and Cherokee is maybe an inch shorter than her, but still looks like she younger than a year, next what do you feed your weanlings and yearlings if they don't have mom around? This one was severely malnourished when the other party purchased her and has put alot of weight on in 2 weeks, so this kinda tells me she is healthy, I am having the vet over today so I am going to get some insight from him but for now I would really like some advice on building her muscle her personality, because right now she is just all gaunt looking, just a sad way about her. Any suggestions?

I just got her yesterday by the way!

She looks about one or two. Just get a vet out, he/she will prescribe for your a feeding schedule along with what needs to be done. And she could be skinny because of her age. You can tell she has a belly on her and her ribs aren't showing too bad. My horse looked almost like her when he was younger.

She's young so you have to expect her to look "gaunt".