I think it's fairly clear that Mab and the Winter Court have no issues exploiting, torturing, terrifying, and killing mortals as part of who they are. If mortals get near them it's just what they do. They do it because they like it, because they think it's the way of things, because that's just part of who they are.
I'd imagine Titania and the Summer Court spend a lot of time countering the elements of Winter that go off and attack mortals. Like Faerie police of a sort. Mab's troops need to be harsh and wild and savage. So they're going to eat/maim/kill/scare anything that crosses them. Titania and the Summer Court are there to stop that happening as much as they can. It's probably a big job.
I don't know that it's a relationship of equals though. If Mab gains more power, Titania should too (at least in terms of personal power enough to take on those of Winter NOT at the Outer Gates). But she isn't handed it. She is expected to go and get it. She is a reactionary to Mab's actions. But it's Mab who has to be proactive about gaining more power, more allies, more favors etc. Remember, Aurora could have upset the balance of power between the Courts by sacrificing the power of the Summer Knight to Winter. Titania wouldn't have had an automatic boost in order to realign things back to equality. It is feasible for Mab, and the Winter Court, to become stronger than Titania and her Court. That's what made the threat in Summer Knight so real. It isn't all that likely though as Mab clearly only gets more power if she needs it, and Titania probably spends a lot of time making sure that sort of thing only happens the right way so she isn't caught out.