Backstory: She comes across as pretty naive and doe eyed, but is actually very practical and streetwise. Her background is, that she was studiying artificing in Baldurs Gate. Her mentor was Zanner Toobin, the leader of the Gondians. She wasn't experienced enough to get caught in the crossfire between Gortash and the Gondians, but she saw, how friends, who worked for the steelwatch factory started to go missing (I know, that canonically we don't know much about the steelwatchers, but it never really plays a role). When her mentor went missing too, she started investigating with the help of some friends.She managed to get into the factory, found out a few things, she wasn't supposed to know and was caught by Gortash. He wanted her tadpoled and put to work, since he needed all the artificers, he could get his hands on, but she escaped. The trauma of the tadpole insertion left her with a short time memory loss of the last days before she woke up. But when talking to Karlach and others about Gortash and steelwatchers, it all came back.
She has an unlikely friendship with Abdirak, the Loviatar priest, who helped her, when her favourite aunt died, who inspired her to get into artificing (forest gnomes are more happy go lucky tree hugger normally). So in this headcanon, his reason for being in the Selunite temple is, that he is looking for his best friend (it's a bit of a big brother, annoying little sister relationship). For this playthrough I recruited him with the help of a mod.
Her motivation is to bring down Gortash and free her Gondian friends. And get rid of the tadpole in her head.
She is friendly, but sarcastic and doesn't take crap. WHen she likes someone, she is very loyal and will help however she can. She herself is not very religious, but she respects others. She makes often good hearted fun of Abdiraks believes, but never in a mean way, because she knows, it's important to him for example.
As for the companions (the playthrough is still ongoing):
I'm going through them in the order, I normally recruit them:
Lae'zel: pretty harsh, but honest, which is totally fine for Lavi, she can deal with harsh. SHe appreciated the giths honesty and also for some reason never even thought, the warrior would betray her - and she was right in trusting LAe'zel. They had a rocky start, but became friends after a while.
Shadowheart: She seems ok, she likes animals, which is always a plus, but her avoiding even the simpliest questions was a bit suspicious. Since Shadowheart seems to approve quite a lot of what Lavi did and said, they overccame their initial distrust. Being a Sharran is somewhat a letdown, but Sahdowheart is pretty untypical for a Sharran according to the people, who know more about that. So she is fine in Lavis book.
Astarion: Well, he is a mess. And not in a good way. Lavi made a big leap of faith and allowed him to drink, but will keep an eye on him. When he tried to hit on her after he said something mean about gnomes in general, she just scoffed and walked away. Does that really work on people? Maybe some stupid town girl, but Lavi was able to see right through his manipulation. She still feels a bit sorry for him, since his master sounds horrible, but she will not let her guard down with this one. She still will help him get rid of his master, if she can. But maybe she shouldn't have let him take the creepy book, now he talks to himself...
Gale: He is fun - a bit crazy and talks too much, but he lifted the mood of the group a lot. Him being a walking bomb is a bit worrying, but then, they have bigger problems. SHe will not let him blow himself up just because a stupid goddess said it. He is her friend and she will help him, Mystra be damned. It seems her respect for religions has their limits, killing freinds is one of them.
Wyll: He is nice to have around and Lavi loves his stories. Still he should have been more open about Mizora, now they have two devils on their trail, the creepy guy Raphael and the not less creepy gal Mizora. But at least Wyll knows, he made mistakes and owns up to them - good start. That he didn't tell her, he is Duke Ravenguards son until they found out, he got abducted, doesn't bother her at all. His family is his own normally and if the cult hadn't dragged his father into the plot, it wouldn't have been important. And he told her directly afterwards, so that was ok.
Karlach: She is her favourite. Good natured and as honest as Lae'zel - a ray of sunshine and great to have around. After Lavis heart got broken, because Nettie wasn't interested in her, Karlach kept her company during the tiefling party and shortly after, the two of them, fell in love. Number one priority is finding Dammon again to get that upgrade.
Minthara: Who? Oh that drow, we killed. Yeah, she was evil, no thanks. (Couldn't find a rpg reason for Lavi to try to keep her alive)
Jaheira: She is awesome. She reminds Lavi of her dead aunt and so is a welcome addition to the group.
Halsin: Well, he is friendly enough, but somehow, Lavi isn't convinced, the city will be good for him. Unlike Jaheira, he doesn't seem to do well outside of nature. Maybe she can convince him, to keep Scratch and Owly save.
Minsc: strange fellow and quite a bit confused, but he seems to mean well. Lavi just wonders, how he managed to survive so long with his childlike mentality. Maybe his hamster really keeps him save.