What kind of damage may have been done by driving with the parking brake on?

My daughter drives a 1990 Toyota Camry. The other day she accidentally drove it about 15 miles (including the highway) with the parking brake on. The weather was over 100 degrees hot. When she got close to home her brakes failed (petal to the floor). At this point she realized the brake was on and she disengaged it. Then the brakes worked intermittently the last few blocks. I suspect they overheated after all that abuse. My husband drove it around the block the next day and the brake were working fine. But now my daughter is scared to drive it again. What kind of repairs may we be looking at?