I scanned through all the posts and am still unable

1)I am on a Tier 2 General and am currently in the process of changing employer.Next week am applying by the premium service.
My wife is already in the UK on the Tier 2 Dependant Visa. Will she have to apply again for another Tier 2 VISA?
2)If yes, will she have to apply at the same time as me or can she applysay after a couple of weeks after i get my BRP.
3)Can someone please shed light on what documents does she need to apply with ?
4) Do we have to prove again that our relationship is subsisting? Like skype chats,marriage certificate,photos? Has anyone applied on a dependant visa from UK? Can you please help !!
