I'd just watch her for a bit longer. Worst case scenario is that cessation of laying may indicate illness. Best case scenario is that she's still laying, but her eggs have been mistaken for someone else's. Do take a look at her poop and her overall demeanor (eating, drinking, socializing) to see...
That's a little long, unless she's having an off season molt, or she's broody (doesn't sound like that though). How is her over all health? Eating, drinking, pooping normally?
Sounds like she doesn't free range, which greatly reduces the "hidden eggs" possibility. My Marans are not fabulous...