I'm no help with the conformation, although I will say I love that stocky build she's got going. That's an STB I could love to own.
I am going to parade rain though with everyone else. This isn't a horse I would pick for someone's first. Especially considering you're still learning, she needs work, and you've got some confidence building to do. What you really need is a chill horse. Something that maybe has some get-up and go when you want it, but can relax when you don't. Trust me. My grandpa purchased an Arabian for me when I was 12yrs old. I got extremely lucky that she turned out to be pretty chill for her breed. Those first few years though? It was intimidating riding her & I was in no means a shy rider. I felt like I had this little ticking time bomb under me that could all the sudden WHAM explode with energy. Me personally, I don't like riding a horse like that. I can't imagine most beginners or people with confidence issues enjoying horses like that. You can toss around the "maybes" or "what ifs" all day long. There's no guarantee she'll turn around to be the horse you want her to be. There's too many nice, cheap horses out there looking for homes that you can BE picky.