I want to give my husband an ultimatum when it comes to his adult daughter
What kind of ultimatum are you considering?
I'm tired of his daughter's attitude. She's rude and a liar.
You need to think about why his daughter's behavior stresses you so much. It is not good to get involved in the relationship between a parent and child. Your input will likely add more stress to the situation.
What do you recommend I do to solve it.
I think maybe you can talk to him about it without her there. And don't be too pushy mention it once and they keep out of it to keep the peace. He can either see what is going or live in denial.