I had a point where I realised my control was slipping slightly and I was asking or negotiating too often, and making empty threats or threatening to tell DH 
Getting it back depends on the basic principle which you and everyone else already know/s - be consistent and have known, consistent rewards consequences and follow through on them always.
Of course that is easy to say and sometimes very hard to do.
Of course you also have to pick your battles (and we all know all this stuff already but forget it in the heat of the moment every day).
I'd pick one thing - say coming in when told. For a while have a strong sanction which you can and will apply if there is argument - for example no TV/ screens for the rest of the evening if you argue at all. Only threaten something you are willing to do - so if no TV and screens will make your evening hell and you can't face enforcing it say half an hour alone in her room, or dock pocket money, or anything you know will matter to the DC in question and you will be able to enforce/ bring yourself to enforce every time.
We also do a marble jar reward system for all 3 kids in combination sporadically, when the group behaviour slips. Set a reward they all/ both want (for example cinema trip or day trip). Marble jar starts half full. Any random good behaviour or helpfulness by any child and a marble goes in, any bad behaviour and it comes out. When the jar is full you have to take them on the promised trip within the next few days, or obviously the jar doesn't motivate next time! It works on the dreaded peer pressure system teachers use in class to a degree but is effective - I don't think it would be if done continually, so I just bring it out once every three or four months when needed.
I emphasise to my kids there are some rules they have to follow so that I can keep them safe - for example staying within defined parameters when playing out, always being where they have said they will be (coming home to tell me if they want to go to a different neighbourhood child's garden than the one they set out for or than the playground) and being back at a preset time or when I call. If they break these rules they go to their room alone for a full hour (there no electronics in their rooms) and are then not allowed out without me for the rest of the day. I hate this as I like them to play out :o but it works - eldest has been allowed to play out for over 4 years and DC2 for nearly 3 and they've only violated the rules once each (and tbh not seriously, just been to a different approved friend's house without coming home and saying first, so they were not where I immediately thought they were when I went to fetch them in). The punishment really worked and sunk in but so does knowing their freedom is dependant on following the rules, and that I have the rules to keep them safe.