Her daughters could be held hostage by terrorists who'll demand that she appears in person or they'll lose a body part per day she we'll still get:
"Tanya sends her love but couldn't make it"
It's often why I think when one character goes in a family it's often very difficult for others as often they go through big moments in the remaining characters lives (weddings, birthdays, medical scares, pregnancy, labour, etc) with their mother/father/sister/brother/child, not being arsed to turn up.
"Your child has been attacked and almost killed the night before their wedding day and now they've gone into premature labour and their life is touch and go for the next 72 hours"
- Yeah but..,,you know....trains.