
I'm not a vet! ;) And of course it'd be illegal for me (and unwise even for a qualified person) to give medical advice without seeing the patient.
That said, usually the runs clear themselves up with a day's fasting, but make sure she drinks fluids -
not milk! You say her gums are pink normally? What happens if you press on the gum and then release - how does the colour change? Has she eaten anything she shouldn't, that might cause a blockage? The straining
could be just due to gripes and discomfort, but she
might be trying to pass something.