Apparently horses are pretty heavy and therefore have stat drops if you carry them, but if you carry them out of the map, you get them free from the horse guy afterward. So yay. That's where most of your other free horses came from.
Aegina is pretty bad at the start with her Wind spell, but it becomes pretty scary if you can get her some Mag boosts, since the damage doubles and pierces Def. You also get some better Wind magic for her later on. In the meantime, she can hit really hard with any Fire spells you buy, but that won't let her get the training for her Wind rank she kind of needs in the long run if you care to use her.