Nebula looks like she's same colors as Thanos but so much of her is different.
Is she an actual daughter of Thanos? If so, can she wield the infinity gauntlet too?
Is she an actual daughter of Thanos?
No. She is also adopted like Gamora. She belongs to Luphomoid species, which is very much different from Thanos'.
From Express article,
A Luphomoid assassin, Nebula was also adopted and trained by Thanos, finding friendship and sisterhood with Gamora in the early years of her life.
If so, can she wield the infinity gauntlet too?
It doesn't have to be an offspring of Thanos to wield the Infinity Gauntlet. Anybody can wield it. This gauntlet is a containment for Infinity Stones, just like hammer-staff of Ronan that had the Power Stone, Eye of Agammotto that had Time Stone, or the scepter that had the Mind Stone. In the comics, Nebula hold the Infinity Gauntlet.
From the same article (may contain spoilers),
In the Infinity Gauntlet comics - a series that directors Joe and Anthony Russo have followed closely for their movie:
Nebula has a pivotal part to play throughout the saga. Nebula is responsible for stealing the Infinity Gauntlet, taking control of the unlimited power herself, resulting in the Avengers, as well as her adopted father Thanos, teaming up to take her down.