Yeah, that's likely too, but generally if she's been sitting for weeks and rejects a non-goer so late it'd be pretty 'ripe' and not too likely to be eaten by her. Did it stink or show obvious rot, or look healthy and normal?
My partridge pekin-silky mixes are reliable at removing non-fertile or otherwise nonviable eggs by the end of the first week, generally, but some other hens of mine will sit and sit and sit until I stop them...