She makes it her business to get to know all her staff.(Macmillan English Dictionary)
The Queen Mother is also a shrewd judge of character who makes it her business to keep an eye on new members of the family and, if necessary, step in to protect her beloved `;firm';. (BNCI)
The lady Alianor makes it her business to discover all that goes on, and has many influential friends --; yet she has made no mention of it.'; (BNCI)