Ok... well...

First stop, then: the pet store!

You can't go wrong by getting something for the dogs! Those dogs are her babies!

Or... maybe...

Something at a sporting goods store perhaps?

Something that would help her when she is walking the dogs. For example if she walks the dogs during cold weather and snow storms... then maybe something to help keep her warm, or keep her from slipping on the ice... or some kind of reflective gear...

Or maybe even just a nice fancy cool looking flashlight for when she walks the dogs at night.

Also... you could try adding a few cute tiny-little gifts along with the main gift.

For example:

If she loves a certain chocolate, but she's staying clear of carbs, then you could give her a little chocolate, in a nice little box, with a note saying:

"I know you're staying away from carbs, but I wanted you to have at least a taste of your favorite chocolate on this Valentines Day!"