You gave her a Dawn bath and used Hartz the same day, right? I'd be more inclined to think the reaction came from the Hartz product. The internet is full of horror stories of dogs getting sick, even dying, from Hartz products.
HartzVictims.org - One More Victim is One Too Many Hartz Products Warning Article - DOG TRICKS, TIPS AND INSIGHTS Hartz Flea & Tick Medicine Warning | Dangerous Pet Products Are Poison & Can Be Deadly for Cats & Dogs