Yes, any builder side user with permission to edit financial information can make a choice. Remember, though, that the change log will reflect that you are the one making the choice under your login – not your client’s.
In situations where the client may tell you on the phone or in person to go ahead with a selection, Co-construct recommends that after making the choice on the selection sheet, you also add a comment such as “Selection made per phone call with Susie Jones today.” That way, you have protected yourself with a paper trail, and if your client disagrees, she will have the opportunity to reply to that comment.