Name: James Anacortes, WA (Zone 8b) (Heat zone - 1, Sunset zone - 5)
If it's not spreading or damaging, it's probably not a problem. Remind her to spray over the plant periodically (rain style) for cleaning and not just water below. Moisture, gunk, and bacteria can grow in those little grooves fairly easily.
I am not an early bird or a night owl--I am some form of permanently exhausted pigeon
