I'm not a horse pro, but I think it has to be 12-14 hands high to be a horse & well she is nowhere near that big, so shes a pony

Chances are she was abused or neglected in her 2 yrs. So in her eyes humans = pain.. Instead of petting her, why not just walk her on a long lead, so she can be away from you, but slowly get to know you. I wouldn't talk to her yet, as your voice might make her think your going to yell & then hit her. Once shes comfy with you walking her at the end of her lead, make the lead a foot shorter & so on.

Mu old friend bought an abused horse & it took us a month to be able to get on him. & then a nother few months to get him to stop bucking & running wild in fear.. We always had a lead on him & 1 person would hold it tight & the other would work with him.

I think you might want to become her friend before brushing her, as getting a kick or 2 is quite painful & ugly!