Tell her not to worry, and hold her head up.ust reassure her that the people in her life who matter understand the situation, and the opinion of the rest doesn;t matter at all.
I can understand how she feels, but in this day and age, separated parents are increasingly common (sad to say) and a lot of families are in this situation.
Your friend is very lucky that all is amicalble on the home front, so tell her to put her mind to that, and not worry what others think.
The moral high ground is a crowded place, but we all live our lives the best way we can - and your friend seems to be doing just fine.