OP, you don’t say whether your DD will be weekly or full-boarding or how far away the school is?
To be honest, I think boarding at 13 is a totally different proposition to boarding at 7, or even 11. A 13 year-old has a good concept of what a week, three weeks or six weeks away from home will actually feel like, whereas a 7 year-old doesn’t really. They can verbalise their feelings; question decisions and, as you say, nothing is set in stone, so if she’s unhappy, you just take her out.
As you say, you have very good reasons and it’s obvious this is not a decision you’re taking lightly.
DS had a few friends who flexi then weekly boarded from 13 and it’s worked out fine. For those who didn’t like it, they left! We live in London and the day schools are extremely competitive, so some board as a way of still getting into a “prestigious” school. Or they cite the sports fields as a reason to board because they spend so much time backwards and forwards between matches otherwise. Fair enough.
Unfortunately, I have, even in this day and age, seen a culture where boys are still “sent away” at 7. At the very first coffee mornings I went to when DS started reception, there were several mums already saying, “Well if my DS doesn’t get into St Paul’s Juniors or Kings College Juniors at 7+, he knows he will board. DH has connections....” This still happens and it was an eye-opener for me. It is a status-led decision, I can’t see what else it is and I can’t help feel judgemental about it. We all draw the line somewhere.