Here's her blurb from the manual:
While she isn't scared to shank a bitch, Nina is far more useful in the back ranks as a healer and item user. Her physical attack is garbage and her defense is nearly extinct. (The game explains this away because her people have thin bones, which makes them more susceptible to physical attacks, but enables flight.) Her lack of attack spells only makes her even more of a burden early on.
Her saving grace is her access to Zom1, which is a sure fire 120 damage to undead type monsters every time. She also has some damn good buffs, including a defense boosting spell by default. She's fairly balanced in terms of speed compared to the rest of the gang, but she will always, always go first on a round where she casts a spell.
Her out of battle ability, flight, isn't unlocked for quite a while, contrary to the blurb in the manual. It's also a massive pain in the ass to obtain. It is useful if you want to complete the map and gain access to some of the training areas, and it's nearly a requirement to find all of the Dragon equipment for Ryu.
She gets the benefit of some pretty nice female only armors, having only to compete with Bleu for them. They typically have some sort of stat boost or in battle effect, most not accurately explained. (a notable flaw among nearly all SNES RPG's, because you get a lot more info out of Kanji in a smaller space.)
You'd think that a person with inherently thin bones would want to be properly covered in combat, but for some reason she spends the game running around in a leotard and thigh high boots. Guess she would be leggy, being a bird and all. Her preference is obviously light armor, and several of her rapiers can be used as items to cast spells, which doesn't consume the item. A worth while investment early on can be a spare ThundrRP to cast lightning spells with. At least it will give her something to do when she isn't spamming heal spells.
Nina's a decent addition to the party, if used properly, but you'll often find yourself devoting resources to keeping her alive early on in the boss fights. After she grows up, she's a bit more capable, but will never be a front line fighter.
Thanks for reading, next time we'll get to know Bo, and what Bo knows.
See you then.