The only solution is compromise. You can't expect her to give up sufficient contact with her children. Children need you whether they are adults or not. In that way you don't understand and you need to be more sensitive. However you have a ton of stressors right now and you need to feel that she is committed to the relationship. You need support during this time and are experiencing stressors coupled with other stressors. You both need to find a solution that you both can live with this. This may include her compromising on her schedule or how it is divided up. You need to allow for her needing her children which may have no particular reason. There has to be a compromise. Sit down and work out a possible solution and then get her to address this to. If you want to be together you will find something that works.
If this has been helpful press accept