How is this hive set up? A deep and a super? If that's the case I would expect to have a fit trying to keep her from laying in the super as long as cells are open there. Using a deep and at least one medium for brood above the deep eliminates a lot of problems but certainly not always. But a single brood chamber isn't nearly enough room for her without and exluder. Or do what your doing now.
"Success is not final, failure is not fatal: it is the courage to continue that counts." Winston Churchill