Silkies and bantam Cochins are probably good choices. There may be more but I'm not as familiar with bantam breeds. Since "she" is a bantam you'll know around 4-6 weeks if it really is a she.
I was wondering the same thing. I also got one at Tractor Supply, in the straight run bin. It is now about 6 weeks old and white. I didn't notice 5 toes though, so will have to check tomorrow to see. Mine looks more like a normal chicken though, like a White Chochin. It doesn't appear to have the fluffy feathers or the blue hue to it. It looked just like yours when I got it though. It will be interesting to see when it gets older.