Not sure? She was born about September 1st and we got her October 6th (she came with the thoroughbred). We're not even sure what kind of goat she is. My wife and I hate goats but she acts like a dog and follows me everywhere. Now we wouldn't have it any other way!
She must be a pygmy. I would guess she'll grow a bit more, but hopefully not enough that she gives your donkey and mini sore backs! I grew up on a goat dairy farm, of course with full-sized goats which are probably about 150-250lbs. Definitely wouldn't want one of them jumping on a mini's back.
Generally it's not advisable to have only one goat because they make more trouble when alone although I tend to think that two goats can be even worse because they conspire. A whole herd may be less trouble but then, you've got a whole herd of goats. Seriously, though, I think they mostly cause trouble because they are smart and get bored easily. Looks like yours keeps herself busy enough.
She (Lola) is the thoroughbreds (River) emotional support goat. If she is too far from him he winneys and she runs back to him. I have to lock her in with the chickens when I work or ride him otherwise she will follow everywhere. Oddly when she is with the chickens he is ok leaving her. She was born in his stall and her mother rejected her so she was bottle feed from birth and they are very bonded.