Yes, her stocking on her back left and front left, and the big blaze and the white going around the muzzle and under her lip are common for horses that carry an overo gene. She more than likely has the splash gene. I bet if you got her tested, she'd be positive.
Perhaps I should test her...
Stella is doing an awesome job hiding this belly;
From the side; She just looks like she's fat from this angle.
Don't she look great for being 18 years old and in foal.