Definitely worth testing her for frame (a.k.a. Lethal white overo) as was already mentioned- not just for what pinto pattern(s) she might be able to pass on, but also to eliminate the chance of ending up with a dead foal.
The roaning and general messiness of the edges of her markings is a pretty good indicator of sabino, but you can test for that to be certain.
There are also tests for Splash and Tobiano patterns, but I'm guessing those would come up negative.
She doesn't look to carry dun (the dorsal appears to be countershading), so I wouldn't bother testing for that.
Testing for agouti can help narrow down what the odds are of getting specific colors, but might not be all that helpful if you don't know the agouti status of the stallion, too.
I don't think there's anything else I'd consider testing for. And I'd go with UCDavis- they had very quick turnaround the time I used them.