CDG airport question

Terminal 1 and 2 are separate buildings about two miles apart. There is no way you can do anything other than clear immigration and passport control, then customs (not much to that) then take the shuttle train to terminal 2 and wait for her there out side of the customs exit where everyone else waits to greet arrivals. You will not have to go through security again, but no way to get inside near the luggage carousels. That is a secure area and customs "quarantine" zone.

There are 6 separate buildings at Terminal 2, so make sure you get the right one to wait outside. If you each have cell phones that work in Europe, she can call you when she lands, and again once she has cleared immigration and passport control, and finally when she gets her luggage and is ready to exit the "green" door. also agree on a back up location like the lobby of the Sheraton Hotel which is at Terminal 2.

I would seriously rethink this. There is no reason to hang around an airport for many hours when you could go into town to your apartment or hotel and get situated, perhaps learn a bit about the neighborhood, and perhaps locate a place for dinner or make a reservation.

You can't hang around security side in an airport. You don't exit through the lounges for waiting passengers as you do on a domestic flight. Instead you are herded through passageways directly into passport control and then out through the baggage hall and then customs. There is no place to hang around and of course your sister wouldn't be able to meet you there anyways since she is in another terminal. Airports are unpleasant places to spend a lot of time.

Hop the train to your lodging and maybe buy a bottle of wine for when she arrives.

I have spent a few hours waiting at CDG, arriving very early for a flight in the afternoon. There are better things to do but not an impossible place to kill some time (in that case, we even had lunch at Maxim's airport cafe, nothing exceptional but a story to tell after the flight). We were leaving from the tiny terminal 2G so we decided to spend our waiting time at the more lively terminal 2F. There is no way you can pass security if you do not have an outgoing boarding card, but there should be something to keep you busy at the departure-check in area of each terminal (the arrival areas, where you will be waiting your sister, are much more streamlined).
What you need to know, is the exact number of the terminal where your sister will be arriving, then have a look to the pattern of shuttles between terminals and a map of how they are laid. When you read that terminal 2 is six buildings (actually, seven), in real life they are very much like independent terminals, each as big as a medium size airport. Terminal 2A, 2B, 2C, 2D (it is unlikely your sister will arrive at 2G) have a single floor, while 2E and 2F have different levels for arrivals and departures. There is plenty to wander around, even if you stick to non secure areas, but you need to know where you are and where are you going.
The fellow suggesting that you should be heading to your accommodation and wait your sister there had a point to consider, in any case.

Not that hanging around an airport is ever a lot of fun, but there is plenty to occupy your time at CDG, including lunch. On the other hand, if you and your sister are staying in Paris and have your place set, you should consider taking the advice to go there and then have your sister meet you.