If her diarrhea is liquid, she is straining and she has a tight belly, then a partial blockage is a concern here. Though I do have to note that we can see straining with lower bowel based diarrhea too.
Therefore, considering all her sign and provided she's not sore, we can try to bulk up her stool and help her pass anything caught.
To start, we can put her onto a light diet like rice with boiled chicken
or white fish. This will be easy for her gut to digest and help if we have a primary diarrhea bug. As well, to help reduce diarrhea further and push that chew through, we can add a fiber source ( ie canned pumpkin, all bran, etc).
If we try this and she isn't settling in the next 24 hours or shows any belly pain,black stools or fresh blood; then that would be our cue for a check with her local vet. They can feel if she has a blockage and test a stool sample. Depending on their findings, they will be able to help get anything caught out of her gut or dispense antibiotics and dog safe anti-diarrheal medication if infection is found.
All the best,