Zyban and Codiene don't mix

My 45 year old Mom  has been smoke-free for the past 6 weeks.  She's still taking Zyban and is also on the patch.  The family has noticed that she is mentally unstable.  She is forgetful, and at times has a hard time walking and driving as if she's been drinking but we know she hasn't.  We recently discovered she has also been taking tylenol with codiene, several a day, for no known reason(which is purchased over the counter in Canada). We are very concerned.  What are the side effects of these drugs in combination? and how can we help?