Deposit/holding deposit and protecting when?

General Discussion

US tenant,still in the states.

AST starts 12th Aug,she arrives 26th

Learning from my mistakes,have asked for a large holding deposit,
Have told her becomes proper deposit when she moves in.

Does this mean I protect it when she moves in or if she sends it by the end of this week do I protect it then although its still a holding deposit.
Don't really want to protect it before she moves in in case something goes wrong.

Have also asked her for 3 months in advance rent plus an admin fee,yes I have learnt

Your comments please guys so I am well covered