Hold multiple dates for a prospective client

Have a prospective wedding client who wants to book but has not decide on the exact date due to various reasons. She wants to pay the retainer/deposit and hold 3 dates (all Saturdays in the fall) for her, for as long as 1 month. Was planning to tell her no, but want to hear if there is a better way to handle it.

Personally I never hold dates. They are either booked or they aren't.

Non-refundable retainer? You can book every Saturday for the rest of the year!

today's lesson: raise your retainer rate.

If they want to pay my $500 non-refundable retainer for three dates, ie lose $1000, sure! Otherwise I'd tell them no, but if I get inquiries for the date i'll let them know, in that case they'd have to book immediately or potentially lose out.

Just to be clear, the bride is serious about booking, but she has not decide on the exact date (she has 3 in mind). She wants to pay a non refundable retainer to hold all 3 dates, for as long as a month, until she decides on the final date.

How likely are you to get inquiries for those dates in the next month? What are the chances you would turn someone away and potentially lose thousands of dollars of revenue?

My policy is I don't hold dates. I do offer to warn people if someone else makes an inquiry, but that's the closest I come. These days i'm quite low volume so if it was a decent sized package I may make an exception, but not for a cheap package.

In our case if it was in the summer, no way will we hold dates. Fall, depends how late into the fall. I would pencil them in, let them know that if anyone else asks about their dates I will let them know and they have 12 hours to book it before I let it go to the new client. We will not loose money because a bride can not make up her mind.

Are the dates that she wants on high demand for your work? If you know you'll have work for those dates, but would be holding off some customers until she decides, it would be one thing, if the fall is an easy season for your work, maybe it would be good to hold the dates.
Maybe deal with her that you'll hold one of those 3 days for sure. Store the dates she wants, and if some other customer wants to use one of those dates, she'll get 24 hours to confirm if that date is good or you'll use that date with the new customer.
Sometimes it's not easy to confirm to a date when you need to check on calendar for the religious ceremony and the pastor/priest/rabii, reception, catering, photog, etc.. She likes your work, so she's willing to book other dates just to be able for you to shoot her wedding. Trying to make a deal that is comfortable for both can be good, but it must let you avoid loosing other potential customers.
I don't know what her date priorities are, but on my wedding, we first needed to confirm on the church availability, then find a place near it that had catering, or hire a garden and then a catering service, then a photog. Maybe it's similar to her, she needs to confirm on other parties before commiting to a date based in a shooting availability.
If someone else says, we're going to get married on this date, you can always say that you'll like to, but you need a day to confirm on a previous arrangement. If this girl says that she's cannot confirm, and it was already specified that she had 24hr notice to confirm on a specific, you can go back to your new customers and tell them you are able and would love to have their wedding.