Story-wise, I like that she's a non-Lord who has a story arc that spans over a few chapters and has an actual conclusion. The fact she has boss conversations with Sonia, brothers, father, and even Nergal is a nice touch. She's also well-connected with other characters in your crew and in FE6.
Gameplay-wise, I irrationally dislike her due to her involvement in Battle before Dawn, where she can sometimes die before you can even reach you. But when you actually get her, look at her bases: 19 HP / 7 Mag / 8 Skl / 11 Spd / 10 Lck / 4 Def / 7 Res. Her very low Con means she will have difficulty doubling all but the slowest of enemies before she gets a few levels, and her measly HP and Def means you have to protect her on enemy phase, and at this point in the game you kinda want units to go out and fend for themselves. Training her up means you're to have to turtle at a time where you probably want to be going much faster with 3 or 4 paladins and 2 or 3 fliers. On promotion she gets D staves and there's not much time to get her to B, which she needs for Physic. Contrast Nino with Pent who starts with A staves and A anima, who has higher HP, Mag, and Def at base than a lvl 20/1 Nino. She's very similar to Erk, Lucius, and Canas at lvl 20/1, but the latter have far better availability and don't need to be babied at all. If you promote them early you can give them staves to level them up even faster (e.g., spamming Mend, Torch, and Barrier). For ranked runs, yeah you kinda have to use her but she's more of a liability than a help, and you'll be using your other magic-users to do the actual work, anyway.
