Tell her you're concerned for her, and ask her if she's considered quitting smoking for good. If she says yes, ask her what you can do to help her. Ultimately, she has to want to quit for herself, or she won't be successful.
My friend's mom had a heart attack (directly related to smoking) and when she got home from the hospital her house had been cleaned top to bottom, walls scrubbed, ashtrays tossed, curtains and windows washed, carpets vacuumed and shampooed...everything you can think of to remove the smell, discoloration, and remiders of cigarettes. Maybe you and your mom could do this together and she can see a doctor to help her control her cravings for cigarettes and break her habit for good.