Long story short, got her to the doggie ER the next day, after she started peeing blood out of her anus (literally
STREAMING blood, like water from a hose). Just prior to the blood streaming, her stool was DARD, DARK brownish-red (looked like tar).
They immediately got her on fluids and started her on all kinds of medication to halt the absorption of the naproxen any further.
Vet/doctor told me if I'd waited another 3-4 hours, that she'd have basically bled to death, internally.