Most Helpful Girl
Just think of this as a very, very lightweight version of real-life priority-setting. Figure out the relevant commitments of time and effort; don't forget to factor in a reasonable amount of alone-time; then just put yr damn foot down, and say that these are yr needs.
If you can articulate yr needs, without being a dick about it, then yr girl should be fine about it. If she isn't, get a new girl, since that one is inconsiderate.
Most Helpful Guy
I think you absolutely can, yeah. But you need to make education your primary focus, and she needs to be on board with that.