There are several different sanctioning bodies ( ASA, PGF, USSSA, etc ). Each is a little different but there generally is not a conflict to sub in a regular season tourney. Your DD is simply written in on the roster for that week and never really added to the team. It's different when you go to nationals as those are not standard rosters or unlocked rosters. If you have a question about a specific tourney ask your coach, but it's usually not a problem.