Quick questions regarding Tier 2 + Dependent visa

Hi,

Recently my long time girlfriend joined me here in the UK. She's studying and I am working full time (under Tier 2 General- Employer sponsored visa).
I am planning to propose to her early next year on a holiday.

The question are, I'm on Tier 2 general, can she apply as a dependent visa with me?
Does she needs to wait for her student visa to expire before she is allowed to transfer to Dependent visa?


My visa is going to expire soon in April next year. When do you think I should be start to apply for renewing the visa?


Thank you in advance.

I'm pretty sure she can only switch her visa (from inside of the UK) after completing her studies