My dog has diarrhea, is thirsty, straining, and restless. What to do?

Poor Dharma, I'm sure you are very worried, but you will be able to get her sorted. So with diarrhoea by far the most common cause is gastroenteritis. This is inflammation of the gut and can be caused by many reasons ranging from eating something rancid to infection. Usually it takes a mild form where the dog will feel poorly for a day or two, but it will resolve by itself. In other cases they will need veterinary treatment as there can be more severe infections etc.
My general advice in the first instance of diarrhoea, is to starve the dog for 24 hours as long as it is drinking and keeping water down. This allows the guts a chance to rest as if they do eat it will simply run through them. Then following this feed plain chicken and rice until faeces return to normal.
Now, if Dharma is in a lot of pain, bearing in mind some will be expected as it is uncomfortable, or she starts to vomit or experiences blood in her diarrhoea, I would take her to the vet as it could be a more serious issue.
Alongside starving her make sure she is up to date on wormer. Many vets sell an over the counter paste which helps to restore good bacteria in the gut, you could give this a go also.
Similar to a human it can take a few days to get over diarrhoea so don't worry overly. However if she is not improving within another 24 hours, or starts to deteriorate, please take her in for an examination.