I would imagine at this age (my son is 21 mos.) that there is quite a range of normal, depending upon various factors. My son nurses 20+ times a day but that number may not be that relevant. Apart from lengthly nursing to sleep, he usually only nurses for a few minutes, enough for one or two milk let-downs. We co-sleep also and I do believe that is a big factor in sustaining milk supply.
I read that in traditional societes children newborn through three years of age may nurse several times and hour and a few times per night, but that doesn't mean that anything different is not normal also. I know just from the achiness in my breasts when my son has not nursed for an unusual duration of time, for him that would be anytime over 1.5 hours. But again, this is likely not relevant as milk composition varies in women, some have richer milk than others, and some children wish for the comfort of the breast more or less than others.
What I did learn though was the more frequently you nurse, the heavier the fat content of the milk, as the foremilk takes time to accumulate, so by nursing frequently, the milk stays more heavy with fat and the fat globules remain in the milk. This is probably going to be helpful when you are able to be with her and can accomodate her need to nurse whenever you are both together. The frequent stimulation will also help sustain milk supply. I also read that baby wearing and having baby physically near your body helps to sustain supply.
You can probably search for 'reverse cycling'. There are working women who do not pump but nurse on demand and also co-sleep when with baby. I have read that many women have successfully kept up milk supply in this manner and addressed their little one's needs of comfort and nourishment also (with other sources when mom is not around).
Where there is a will, there's a way! Good luck, please keep us posted. Oh and best wishes with school and classes