Anything (ANYTHING) in the Solanaceae family should be avoided. This is also the case if you have small children running around.
A lot of people would hesitate to even call them 'entheogens,' because they are extremely toxic. Datura of all species, Mandrakes (also called May Apples), Nightshades (members of the belladona group) and Brugsmansia (sp?) all contain a triumvirate of highly dangerous molecules called tropane alkaloids. That include atropine, scopolomine and hyoscyamine. These three are the most powerful known anticholinergics in existence.
I won't get into the pharmacological effects, because I know we discourage that kind of talk here, but believe me, it is NOT a fun way to go.
Not all members of the Solanaceae family are toxic in all parts, but if you are going to be buying one, make sure you do your homework. The 'interesting' ones are all pretty poisonous, however.
Fun fact: the word 'tropane' is derived from the name 'Atropos' who was one of the three fates in Greek mythology: she was the one who cut the thread of life, causing her victim to die and enter the underworld. This should tell you something about the bad juju that lives in these plants.
If anyone wants any, see my signature
EDIT: I would stay away from salvia divinorum, also. I'm not sure if it would have the same bizarre effects on a cat as it does a human (I don't know about the opioid receptor structure of cats), but I can't see why it wouldn't, and having a salvia-d cat running around sounds dangerous for both the cat, you, and your lady friend.