She consistently stops the wrongdoings of others (party members mostly) and attempts to steer them in the right direction (which is difficult considering everyone wants to be as chaotic as possible).

You at odds with group. Do they enjoy this or find it irritating?

My party members, despite some of them being some form of "good", always go along with him because they want more loot.

You at odds with group, who seem to prefer following his style. Does that make him think you're derailing the group?

Finally, a break from having to be the mom of the group!

You at odds with group.

new character hates my monk right off the bat. He argues with me at every point possible, works against me constantly, left me to almost die alone in a prison, and actively tries to turn the group against me.

Player problem but does it stem from him thinking you're the one derailing the group still?

And I've come to the conclusion that I need him kicked from the party or killed somehow (in the most lawful good way, if possible)

Player problem, and you thinking of mimicking his game actions. Do you think the reason he's singling you out and trying to get the group to turn against your character is the player also trying to 'solve something in game'? Player problems, talk openly and politely.

He has continued this trend and the last five sessions have been exhausting. It doesn't make sense that he is friendly and civil to every other person but me

Player problem, and your character singled out being different from group.

I'm tired of spending most of the session trying to stop him, and don't want to give up

You at odds with his character, repeat of being the mom. Does your character fit with the group?

I am already afraid that he's going to do the exact same thing

Player problem. Discuss it openly but politely, don't try to solve in game.

our npc faction leader is also LG and I've started trying to convince him of the thief's evil intentions in an attempt to get him kicked from the group

That would just add oil to the fire.

I really dislike this guy as a person.
I'm enjoying the sessions less and less because of [his characters]

I think you guys need to have an open but polite conversation about issues, no weird social maneuvers that take place in game. It sounds simple but it's not easy to do, but it's important to defuse in game tension.