I think it is possible but if she has never been ridden, it may take years to get her to the point where she is suitable. That is, of course, whether her temperment under saddle is suitable for a child to ride or not. Some horses that are sweet as they can be are absolute terrors when you get into the saddle and others are just as sweet to ride as they are to handle.
Has she ever been ridden or just been a broodmare all her life?
Has she ever been ridden or just been a broodmare all her life?