You're probably looking at more of a possibility of pancreatitis than long term effects from the garlic.
How long ago did she help herself to this pizza?
Garlic can contribute to certain blood problems (anemia), but the size of a lab compared to the amount of actual garlic on a pizza will not likely be a problem.
Still, each animal is an individual and you need to err on the side of caution.
You've got a choice to make here. You can either induce vomiting or you can take the chance to wait this out and have her checked this week by her vet.
To induce vomiting first make sure you're doing so in a safe area that will be easy to clean up and easy to examine the vomit.
Offer your girl 1 teaspoon of hydrogen peroxide (it should be fresh) delivered to the back of the tongue. An eyedropper or baby medication delivery system should do it better than trying to use a spoon. If you must use a spoon, enter the mouth through the side rather than the front, gently holding the animal's chin slightly up with your other hand. Having a helper would be even more efficient, but do what you can with what you have.
Don't do this more than two or three times. Look for the remnants of the pizza in the vomit.
If you have activated charcoal specifically for instances like this (all pet owners should have this at hand), make a slurry (like a thick milkshake) and get it into your companion.
If you do not have activated charcoal then burn a couple slices of toast - very, very burned. Crumble and try to get her to eat this. Although she might be a bit full from eating your dinner
Call your vet for a follow up visit.
If you don't choose to induce vomiting, I'd understand that too. You'll need to watch for signs of bloating (more from the pizza dough than the garlic) and discomfort. She may even vomit on her own throughout the night.
If you can get her to stay calm, be comfortable and get through the night without incident, at least putting a call in to your vet tomorrow is worthwhile.
What you're going to do about your own dinner, I don't know