Are you sure she wants the second side?

For me I only let down once a feed & both sides let down at the same time. Once that happens milk is flowing & ready to go on both sides. If she has the second side I don't let down again, unless, as you said, its half hour or so later.

DD will fuss at the breast for me if she still has a belly ache. She won't usually stop feeding til she's well & truly full, which unless its cluster feeding, is only one side at each feed.