Do slow feeder bowls actually help cats?

For the right cat, yes. Slow feeders and puzzle feeders make a fast eater work for each bite, which cuts down on the gulping that leads to vomiting right after meals and adds a bit of mental enrichment too. They help most with kibble and with cats who bolt their food. They’re less useful for wet food, which gets messy in the maze designs, and they won’t fix vomiting that has a medical cause. Start with an easy design so she doesn’t get frustrated and abandon the meal.