mine also goes out every year on 24th, as it is also her holiday on 25th she doesn't come back until her holiday is over. Because I go out on the 31st every year so she has to stay. If you are not comfortable to let her go then don't, but if she is willing to come back 2am then I think it is ok.
I think she is attending St. Peter & Paul's Church. You may take reference here of all the time schedule for the special Mass on Christmas & New Year. (click here)
I will only allow my helper to go to special masses, which is not on her holiday, if I don't need her. I'll try my best to let her go, but it never be a must and not a promise, even not a practice and take it for granted. She must know about it.