mix (one) up in (something)
To involve or embroil one in some situation or circumstance, especially that which is problematic, unpleasant, dangerous, etc. Often used in passive constructions. I can't believe I let you mix me up in another one of your cockeyed schemes—do you know how much this is going to cost me? I don't want Sarah getting mixed up in any of your boss's illegal dealings, you hear me?
mix someone up in something
to get someone involved in something. Please don't mix me up in this problem. Walter mixed up his daughter in the sordid affair.
*mixed up in something
involved in something, especially something wrong or illegal. (*Typically: be ~; get ~.) The youth has had problems ever since he got mixed up in a group of boys that stole a car.