I believe if they aren't in therapy they should try before doing the dance with a lawyer. If he is not doing his 1/2 of the parenting, then a response she can state is I need foreplay which means 1/2 of the household/parenting responsibilities.

No foreplay = No Sex

If he reciperocates then after she has regained some sanity and reserves, she will need to work on what it will take to be in a position to accept his sexual advances (or) make advances herself.

Other's have called out excellent resources to use, but some simple negotiations around intimacy (presuming the earlier bits are done) for example. We promise to have sexual engagement X times a weeks and both parties are required to have Y orgasms.

So if they promise 6-8 interactions and they both receive 6-8 orgasms, then a base could be built. The most important thing is though ... she needs to be able to orgasm in her own way and in a way that makes her comfortable.

If he refuses, then get the divorce as he isn't worth it (on any actions). If she doesn't hold up her bargin then she is at fault ... if they divorce they have both failed ...

When it comes to him doing the work presuming the kid is safe ... she should be hands off and should be taking the time to relax and recoup.