Forum:A question I hope a developer might answer about little sisters in Bioshock 2

I have a quick question I hope a developer can answer or any one else with knowledge of Bioshock 2, can you adopt multiple little sisters that will gather ADAM faster, or will you have to harvest them if you already have one. Or another theory, will the little sister take the little sister every fight regardless of how the fight goes(she's a lot faster than you)