Totally wrong and I've been there. . .
She needs to go and say now that she will not be working these days, shes done her bit, and some of the others will have to take up the slack now. Some of those little kids will have grown a bit up by now and if you work in an area that needs to be staffed over the holidays you have to expect it and not use children as an excuse.
Long personal rant here feel free to ignore
Mine was the bloody NHS (yes I fully support it, but it wasn't supporting me at the time).
I worked nights every Christmas Eve/Day/Boxing Day for 10 years, because my family live abroad and you couldn't have annual leave over Christmas so I never saw any of my nieces and nephews open their presents etc. They all have lovely memories that don't include me.
Even after I got together with my OH it was still assumed that we'd want to be out on NYE, our idea of hell. But I carried on being a bloody 'team member' & 'taking one for the team'
Then my Dad was diagnosed as terminal given 4-5 months which included the Christmas period, and I was granted annual leave, well I told them I was taking it. I was not missing my Dads last Christmas.
The in the Nov we had a new starter who couldn't believe he'd have to work Christmas because of his 'kiddies' (his words). He was told he have to ask someone to swap, the rota was done and he'd been told he'd have to work it at interview.
He then spend the next 3 weeks trying to emotional blackmail me and the ward manager. She broke first and asked/told me I had to consider it. (Never mind that I was a senior and he a junior which would have left the shifts unbalanced and they would have to get another senior in to cover the shifts I swapped with him.)
I contacted HR and handed in my notice the next day, which because I swapped and canceled leave so much for others meant that my notice period was under 1 week, which left them totally up the shitter. I also implied that I would be going to the union to discuss bullying, and a hostile work place.
All the staff knew the reason I was given leave, and I was still made feel like the bad guy. Slightly changed when it came out the kiddies were about 10 & 12, and he was only doing a half shift (6 hrs).
And they wondered why after this (and shitty behavior when my Dad died) I left within 3 months. To a much better job where being a team member means you get to take occasional as well as give.
I'm still nearly 8 years on being used as a reason why they don't give A/L over Christmas, no mention of the previous 10 years.
Sometime you have to kick off, you let yourself get walked over too often it becomes the norm.
Wish her luck for me and tell her to kick ass!