My 8 year old daughter has been working on the axel on and off for a year. Has passed Juvenile moves, doing well in precision, passed 4 ice dance tests in a month - so all else seems to be going well but getting this jump. She has successfully landed it several times, but not enough to say she's really got it. The axel is usually the first jump that takes considerably longer than the previous jumps to master. I personally know skaters who took well over a year to land the first one and another year before the axel became a consistent jump.
Every skater is different when it comes to the axel and then the double jumps.
If skaters are doing other things, such as precision and dance or even school activities, it will take longer. Try not to put alot of pressure, even unintended, on consistently landing the axel. You didn't say if your daughter is getting frustrated about the axel. If she is, it may be time for a change. She may need to work on something different for awhile, perhaps another jump such as the double salchow or double toe loop or new spins.