Bob; as you can tell, there are a lot of different opinions. Some people find the issued boots comfortable from day one. Some, like the cadre speaking to your daughter, recommended breaking them in. Each person is different.
My son brought one pair with him. He has/had the luxury of living at/near an air force base, so getting a pair wasn't difficult. He broke them in ahead of time. He did say that they wore pretty nicely from day-1 and didn't really need to break in. He did, as the Pamphlet stated, have to carry them with him the first day, along with his back pack and AOG goodies given him. In retrospect, he said he wouldn't get them early. But as you can see, everyone is different.
I recommend going to BCT with as close to the "Clothes on your back" that you can do. "LITERALLY". A typical school back pack that you can fit an extra change of underwear and toiletries, and your paperwork in is all you need. If you have to wear the same civilian cloths a 2nd day until you get all your uniforms, SO WHAT. Don't worry about boots.
On a similar/side note: Hopefully you made a copy of ALL PAPERWORK that you did through the appointment process. My son sent in the original of everything he had to, and had 2 copies of EVERYTHING. Including medical records and immunization records. We kept one copy at home, and he brought a copy with him. So, when they say they didn't receive a certain piece of paper, he simply handed them his copy and didn't have to go through any hassle. One cadet last year took such advice and patiently watched as a couple new cadets got more immunizations because the academy didn't have his records. He gave them his copy and didn't have to get new shots or fill out the security paperwork. Anyway; RULE #3242 in the military: (Actually, rule #1): Make a copy of ALL PAPERWORK and have it available if needed. best of luck. mike....