one more clarification

If you are added to her application now before her 485 approval, you are her derivative and you will NOT be considered 婚姻綠卡. It is still employment-based green card application, you are just deriving the benefit because of your relationship to her.

If you marry after her GC, then it will be considered 婚姻綠卡, and as a result, your priority date will be the date of your filing.