Yes some breeds do start laying later...Marans being one and sometimes EE's too.
Plus it's winter and if you haven't been providing supplemental lighting, you'll have to wait a bit longer.
Do you free range, might she be laying out in the range area?
Are you positive she's not laying? You're probably expecting a green/olive egg but if a blue egg gene from the EE didn't come thru, she may be laying brown.
ETA:
How does her comb/wattles look:
Plump, shiny red - usually means laying.
Shriveled, dryish looking and pale - usually means not laying.
Have you checked her pelvic points?
2 bony points on either side of vent:
Less than 2 fingertip widths apart usually means not laying.
More than 2 fingertip widths apart usually means laying.