When I brought my new horse home about half his mane was gone and he had really ugly dandruff. The hair that was left was thin an fine and his skin dry and unhealthy. I roached the mane and poured vegetable oil on it and rubbed it in about two or three weeks ago. It's about 2 1/2 inches tall now and thick and luxurious. Gilly was half Fjord and his mane stuck straight up. I just kept it roached. I like the clean look although I will allow Trampus's mane to grow out. Jimmy Williams at Flintridge Riding Club in California got tired of messing with manes and roached all of his show jumping horses. He was famous and could get away with it.
I'd keep her's roached if she didn't have such an ugly thin neck. Even with muscle its still pretty thin. :p I'm doing a baby oiling solution that has been helping since I got her, but still haven't gone to the tack shop to get some MTG.
Sorry either you cut it again or let it grow. I like to leave my mare's mane long and natural. It may take more time to groom but no worries about it going through that awkward growing stage where you don't know what to do with it.