If your occupany is already full for the room and she is not on your reservation as part of your group and you are not there to personally give her a key, No they will not give her a key to your room.
Your only option is at check in to ask for an additional key without any tickets attached to the key. I am not sure if they will even do this, since now all keys have a name attached to the key, this is why they want to know the name of each guest in the room, regardless of whether you have tickets on the keys or not.
All I can suggest is ask at check in and see what they suggest. See the problem is if they give her a room key and your occupany is 4 and she is the 5 person then she could use this key for access to Extra Magic hours, etc. I know this is not your plan, but this is one reason they are more particular now that everyone including kids have a key with their name on it.
My only other suggestion is to pretend you left something in the room, and leave the Moms with your wife and go meet your sister and let her in the room. Of course she will be a captive as she cant come and go.
I am not sure with your having a Lodge room they will give you another key with a different name on it and having your passes on the others complicates things for you.