To some extent, it's a matter of them getting old enough to leave them alone, and for the hair to get long enough/thick enough to hold the topknot in.
What are you using to put her hair up? I find the best thing for everyday to be the teeny, tiny "Scunci" style covered elastics. these don't stay in the best, but they break the hair the least, which is important for everyday.
For shows, I use the VERY tiny bands from Sally's that say they won't break hair. They might in a child's hair, but if the dog starts working on it, they hold tight enough that the hair definitely DOES break! But I find that when Kodi is in his crate (or working) at a sho, there's enough going on that he forgets about his hair and leaves it alone!
Karen & Kodi
(Starborn Kodak Moment BN, PCD, NA, NAJ, CDX-C, RE, RL1X3, RL2X3, RL3X2, ARCHMX)