Think about that Destin - free photos for advertising
and framed prints?? Figure out a value for using the place of business for a day and offering photos to customers, what is that worth? Is it the same as what it will cost you to print and frame photos for her to use to decorate her place of business?
It doesn't cost
nothing - there's value to your time, the camera/equipment (which was hardly free), the time spent learning and practicing and developing skills - as well as the time that should be spent on developing expertise and learning how to do contracts and licensing and pricing, etc. etc. This is why I think pricing for creative work can be challenging.
Get on
American Society of Media Photographers - Homepage or PPA and start learning how to do contracts, etc. Both of these pro photographers organizations I think have links to the same price quote resource. Even if you work out something in trade you'll need to contract usage of the photos. And I wouldn't give her
all the photos - provide select photos for her promotional use.
I'd think about a special discount for the day for customers who get pet portraits done, then go back to your regular pricing. Otherwise this is a day's work for free plus time later spent editing, getting the photos out to customers, etc. all done for free. This should be worked into a business plan, or if you don't yet have one that's something you could work on. Otherwise you might find you've spent more time working for free than making any money. Which is fine if it's for a charitable cause such as a rescue shelter, etc. and it's your choice to donate your time and ability to charity.
edit - If she doesn't want use of the photos then you're apparently going to be working for free (giving free portraits to her customers for the day) and paying her, and she benefits if doing this brings customers in which helps her make money (which has value) - so you better determine how much you want to spend for promoting your business.
ASMP does webinars, no cost and you don't have to be a member; you may want to see if they have any coming up that might be helpful.