So let me ask slightly different question. Are there any tips people have for a couple getting a divorce
First, don't acquire a girlfriend until your divorce is really final. If there was any intention or possibility of reconcilliation it will certainly be made more difficult. In fault states you could be materially hurting your case, in non-fault states you could be establishing a pattern of behavior that could be used against you later if you end up in court. Even more so if kids are involved.
Second, try for a non-adversarial split and divorce agreement if that's where you are going. There are mediators who specialize in this. Lawyer fees can easily exceed the value of what you are haggling over.
Third, no agreements count for anything except the final decree.
Fourth, I suggest you try to be honorable, but don't trust that your soon to be Ex will be. Divorce and money both have a way of bringing out the worst in people sometimes. Try not to stoop to that level if you find yourself in negotiating hell, but equally try to be alert for bad faith. Note: some lawyers seem to think it is their job to try being as adversarial as possible, up to and including dirty tricks. If you see that developing from either side, you'll want to try to cut it off before it gets out of hand.
(Beware, there are financial complications such as tax treatment of different kinds of assets that most divorce lawyers and even financial planners don't understand and will confidently steer you wrong.)
Fifth, if there are kids involved their welfare should take precedence, but very few adults (especially divorcing adults) seem to be able to make the leaps involved to understand that.
And --- nothing about divorce --- as a general rule, co signing a car loan is a bad idea. If the would be buyer cannot swing the credit to qualify alone, then they should consider another vehicle. Aside from the rare instance where a co-signer is helping a young adult get credit established, this should be a red flag. In a divorce (actually separation and a girlfriend on the side) this should be unthinkable.