Teresa I'm sorry I must have gone to bed last night right before you posted this so it might be too late but here goes.
Lobelia isn't something I would think about using for what ails your sister. It sounds like she might have what they call a 'dry socket' which can be extremely painful. What I would do is make a Slippery Elm paste and pack the hole with it as well as she can considering that its probably got stitches in it. She could slather it all over the sight and just let it sit there. I'm not sure how good it would stay but I think it would really help.
My husband had to have oral surgery to have 7 teeth removed a little over a week ago, he didn't take the anitbiotics or the pain pills but we knew this was coming months ahead of time and he'd been loading up on extra Echinacea and garlic big time, I KNOW that helped tremendously! I had the Slippery Elm at the ready just in case but he didn't have to use it.
In case the dentist didn't tell her, she shouldn't be drinking through a straw or drinking any soda products like coke as both those things have a tendency to cause dry socket. Sometimes people get dry socket even though they don't drink through a straw and drink sodas.
I hope you've got some Slippery Elm because I think it would give her some relief. Please let us know how she's doing.