OK. She is pretty young to have stopped laying entirely. Here is a thread with a tremendous amount of information about what can go wrong with this system. A lot of these problems are serious or terminal, of course. However, in particular, see Speckledhen's post #26...
When did she lay last? Does she ever lay soft shell or shelless eggs? If you think she could be eggbound, give her a warm bath, and read here:
https://www.backyardchickens.com/forum/viewtopic.php?id=32648&p=1
https://www.backyardchickens.com/forum/viewtopic.php?id=22308
How high is the...