Need an advice!

I would say that it depends on what you want to do.  If she absolutely insists on being able to keep the stand, and you don't mind buying one, I would charge the full cost of the stand plus the time it takes you to purchase it, etc.  If you let her use one, then you can charge an rental fee that includes cost of delivery and pick up of the stand.

When I have a client needing a stand I require a deposit that equals the amout of the stand replacement should I not get it back.

If it is someone I know I allow them to give me a check , which I hold and return upon receipt of my stand. If the stand is not returned , the deposit is forfeitted or the check is cashed to cover replacement.

I do not charge a rental fee if they have purchased the cake or cupcakes from me.

Agreed...customers usually don't want to keep the cupcake stand, but if they do we charge the replacement cost of the stand plus normal markup. For rentals we charge the replacement cost as a refundable deposit plus one-third the replacement cost as a rental fee.

Another option is to have the customer provide the stand, in which case there is no charge as long as they deliver the stand to us before the event.

You can also make a cupcake stand fairly inexpensively and tailor the design to the design of your cupcakes if you want. Just charge the customer for the materials and the hour it might take you to make.  That's what I did for this order.

 

http://cakecentral.com/g/a/2231476/welcome-brooklyn/

 

You can find steps online, but I followed these instructions.

http://cakejournal.com/tutorials/how-to-make-a-cake-stand-for-cupcakes-or-mini-cakes/

 

I bought white cake drums in the size I wanted, wrapping paper to match the theme, cake dummies, colour coordinated ribbon a glue stick or hot glue gun.  Because the cupcakes are in papers/liners you don't have to cover the decorative paper in food safe plastic if you want want to.  I didn't and the paper did show some grease marks.  You need enough ribbon to wrap around the dummies, so make sure you buy enough.  It was a pretty easy project.

I have several cupcake stands that customers can use.  All of them are ones I get back when they are done.  I have the client pay a deposit fee that they get back when the stand is returned in the same condition it left in AND in the time restraints according to the contract.

 

Remember, that in Ohio you don't charge tax on food items not eaten on premise (as in your house in your case) but you do charge tax for delivery fees and rental fees.  The tax rate is based on the city you deliver the goods to, not the city you are based in.  So, make sure you look up the city's tax rate you are delivery too before you give the final price.  And of course, just make life more annoying, the tax rate can change mid year so keep checking through out the year so you don't have to pay more than you received because the rate went up and you didn't know.