She's taller than 75-90 % 12yo girls, and heavier than 25-50% of them. Whether that is "healthy" depends on how she takes care of herself, and how she was growing up until now.
If she is built like other members of your family she's most likely fine. But if her weight was on the 75% and now is on the 25th, there's an issue. Ease your mind: discuss her "growth chart
" with her pediatrician.