If she's not staying in a concierge room as a registered concierge guest, then no, she's not entitled to join you on the concierge floor. You are not supposed to bring "guests" to the concierge lounge. The floor is keyed, and her room key will not allow the elevator to go to the 6th floor.
Also, not sure how old she is, but guests under 18 are not supposed to stay in rooms at WDW unless they are either connecting with a room with adults in it, or sharing the room with an adult.
It's very likely she won't even be on the same floor, or possibly even in the same part of the resort, so having her along to help with the kids would almost be moot if she wasn't close by.
At the AKL, If you are going to the expense of a second room, you might want to consider a 1BR suite. Some have 2 queens in the BR, plus the sleeper sofa in the LR. The cost would probably be about the same as the two rooms. Just a thought.
At teh Swan she'd be at minimum five minutes away, and would not be allowed to come to the concierge lounge with you. Remember, you check in with the concierge, so they DO know who is in your party.
It sounds like you maybe just want someone to help wrangle kids at the parks--it might actually be a LOT cheaper to hire a sitter from down there from Kids Night Out of Fairy Godmothers--you might want to look into that--even at $15 per hour for 10 hours a day, it's still going to work out to less money than brining your sitter I think.
Anne