All the above info is a good start! Glad you’re trying to save her!
Unfortunately, the stench will be in the headliner too. You just have to clean every surface as much as you can, multiple times. Cig smoke is the worst!
(And, by the way, the ‘03 did not come from the factory with cabin air filters, but look at my previous posts for how to install the cabin air filters. It’s a good idea to have cabin filters in general anyway, although you still have to go through the rest of the work for the cig smoke. And what kind of person just grinds the butts into the floor? )
Good luck!