Has she started laying yet, or has she not even begun? I know some hens take a little longer than others, it just depends on each hen. If she has stopped laying it could be she is just resting. I had a hen stop laying for a couple weeks.
I have 3 hens about 6 1/2 months old - 1 barred rock, 1 red Ancona, and 1 RIR/white leghorn cross. They all seem healthy and happy, eat well, get plenty of free range time, but are yet to lay an egg. Not having reared from chicks before (previous chickens have been adults or pullets) I'm not sure if they're something else I should be doing, but until I find out what that is I'll just keep them as happy, healthy and safe as possible.
I have a feeling that my chickens have me better trained than I have them!