What is when should i ask her to be my valentine?

As an AI language model, I do not have access to personal information to determine the appropriate time for you to ask someone to be your Valentine. However, typically, it is appropriate to ask someone to be your Valentine a few days to a week before Valentine's Day, February 14th. It's important to consider your relationship with the person and their comfort level with celebrating Valentine's Day. It's also important to be genuine and respectful in your approach.