If it took you 4.5 hours to ride 42 miles, then every 10 miles was approximately every hour. That's not all that much for food or pee breaks. Of course, if you were traveling at 20 mph and stoped every 10 miles, that would be more 'excessive'. And if each break is 20 minutes, then yeah, that would be really annoying, too.

I think if you do want to stop less and ride more, I would suggest two things. 1) suggest to keep the breaks shorter or 2) suggest that she could eat on the bike if she must stick to such a regimented nutrition routine? As far as the pee breaks...I'm not sure what you can do about that.