From the client's point of view, it's not a bad move. Lock in rates and whatnot before anything (as far as economics) goes haywire, or if she pays now, just in case she is sure that she will have someone to capture the memories already paid.
(From a financial standpoint, the latter is not bright but I've seen people insist on paying me in advance because they want to be sure they have me. I usually turn it down, I'm a "pay me when I show up for the actual gig" kind of guy, don't really believe in deposits because I haven't reached a point where I'm losing major flow unless it's a large profit event or I'm not comfortable with the client. Right now I'm losing bookings because of the SAT and AP tests

)