I have lost only one cowplant in Sims 4, and she was my first. I was very heartbroken when Betsy died (yes I named her). I fed her every day, but other than that I didn't interact with her much. I was so afraid that she would eat someone, so I had her locked away in the back yard.
All the other cowplants that I have had since they all get fed like Betsy, but one thing I do differently is I make sure my sims interact with them quite often. I also keep garden plants in their area as well. As far as danger, just make sure as soon as you see them stick out the cake slice, have someone one feed the creature. If someone does be dumb enough to attempt to take the cake, they will get eaten but will get spit back out again. The danger would be if they tried it again before the negative moodlet cleared up.