I would bet that her egg size improves. The first eggs a bird lays are their "pullet eggs" and are almost always quite tiny. Give them time, either RIR or Production Red should give you large to extra large eggs eventually.
I didn't mean to imply that hatchery birds are bad in any way--the majority of mine are hatchery birds. I just meant that since the OP was sent a RSL as part of his mystery brown egg pair, the complement to that pair might be a Production Red, especially as the red on the bird in the photo...