really, it should be six, to correlate properly. young Lady Winter, fair Queen Winter, old Mother Winter, young Lady Summer, fair Lady Summer, old Mother Summer. Each of them have their own names and each takes about two months of the year, breaking the seasons into autumn, winter, thaw, spring, summer, harvest. approximately.
 
Summer (Seelie) is lively and wholesomely beautiful, but remember that predators thrive in the summer half of the year, too. You’ll see teeth and a grinning smile as you go to your death with them.  
Winter (Unseelie) is also beautiful, but harshly so, like a blade of glass. The threats there will kill you in a far less personal manner than Summer, with a chill wind or claws in your back, because it’s about survival first.
 
Neither half is evil, per se, but both have a tendancy towards cruelty. Summer is much more gentle with their tortures, and often don’t see them as such, but Winter will tell you they’re going to cut you, and enjoy it, because why dick around and confuse things?  
Both sides will be circumspect about their scheming, though, but Winter is better about roundabout and Summer is better at covering their slightly-more-straightforward methods.
 
Remember, ascendancy of either is bad! Eternal winter is terrible, but a perfect Summer would be an apocalypse, too. Year-round fertility and bounty for everything? Awesome, especially if you’re a virus or bacteria.

Ah, so she’s based on the Sidhe. Then shouldn’t she only be Titania during the summer, Mab during winter, then someone else entirely between the two during the transitional seasons?
 
Or would Titania carry on into fall and Mab into spring?
 
…I’m not that well-versed in the fae.