Scared horse, please help?

this guy has 3 wild horses (2 stallions and a mare who is pregnant), the SPCA saved them, but they are in such a bad condition, so they are going to put them to sleep next week. I really want to try and help the mare because she is pregnant. What can i do to get her a bit tame, then maybe they'll see shes at least manageable. The problem is that they are 3 in a training ring because you cant work with them. They aren't halter tame or anything and you cant get near them. Please what can i do? If i cant get the mare tame even a little bit, she and the baby are going to... I really want to help, and if i cant succeed at least i know i tried.