"She got all the fluids, and pain medication and antivenin, but she likely got more of the venom. Because of the previous bite and her age, her heart just gave out," said Sweetwood.
Sweetwood lives on a canyon but says rattlesnake sightings are very rare near her yard.
Across the county, County Animal Services says rattlesnake calls have jumped significantly this year. Sweetwood's message for other dog owners: look into snake aversion training, something she now wishes she had done for her Sadie.