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If your wife is a dependant on your Tier 2 visa any changes you make such as applying for a new Tier 2 visa will affect her previous dependent visa and you will have to include her in your new Tier 2 visa.
I am not sure why your friend would be making enquiries about your immigration visa to the Home Office and not yourself making the enquiries. If your employers are both under the NHS, why then are you required to make a new Tier 2 visa application? Your wife is a dependant on your previous visa. If your previous visa becomes invalid or expires all dependents on that visa by common sense becomes invalid.
You should seek legal advice from a Solicitor or an Immigration Lawyer as the answers given here are general answers and not legal advice that you can rely on. JustAnswer is not the appropriate place to seek legal advice.
Well the answer to your question is if your visa is changed it affects all dependents on the visa. You should seek legal advice.