I recently had a similar situation as you. I planted 2 reg fem strawberry cough seeds, and 1 northern lights auto. I ended up mixing them up, not knowing which is which. The whole time i thought i knew which ones were the strawberries and which one the auto was. To my surprise the auto turned out to be 1 that i thought was one of the strawberries. Unless you've grown either of the strains before, theres not really a guaranteed way to tell. But don't sweat it sooner or later the auto will start flowering and right then and there you'll be all set and know exactly which one she is.