You certainly could hope for eggs from a hybrid like yours by 26 weeks, but it's not unusual for some pullets to go beyond this. As Chuck says, she may also be a week or two younger as well. Also, at this time of year, the daylight is getting less as the evenings draw in, and the loss of those hours of light does make a difference to the age at which pullets can make it into lay. Those hatched in early Spring do their growing during the months when there are long hours of light, and get into lay correspondingly early, but those hatched later in the year don't get this stimulus to such an extent and are often slower to mature. Some don't make it into lay before about November, and these birds often wait until the next year to being laying, especially the purebreds which are usually slower maturing anyway. Also, as Chuck says, unless you have reared a bird yourself, you can never be sure what challenges to her health she may have had to overcome as a chick or grower.
So don't give up hope, try to stay patient, this every reason to suppose she'll come up with the goods within the next 4 weeks or so. If not, she will grow on slowly and steadily throughout the winter and will be a good strong hen who will probably be an excellent layer next Spring.
