Your friend is right. Lilies are indeed toxic to most reptiles including snakes. They can cause illness up to and including death. Lilies shouldn't ever be included in your reptile's viv, nor is climbing on them a good idea.
In addition, lilies are highly and I mean HIGHLY toxic to cats. My daughter is a veterinarian and she has treated too many cats who took a sample nibble of a lily in a bouquet. It doesn't take much to be fatal to felines, nor too long since ingestion for treatment to be unsuccessful. She's said that even brushing against the flowers and later licking pollen of their fur when grooming. I love lilies, but I love my pets more. I steer clear of true lilies (the Lilium family) and day lilies (the Hemerocallis family). O
Note: the common houseplants which are often known as "peace lilies" (Spathiphyllum) are fine.
Sent from my SM-A716U1 using Tapatalk