I agree with "m0use". It looks like honeydew to me. That is, sugar excretion from sucking insects such as aphids or whiteflies. It fits with the fact that the lady was standing outside. A. californicus is great against spider mites, but it doesn't help much here.
What I would do:
-Separate the plant.
-Thoroughly wipe or spray the undersides of the leaves with lukewarm water + a little insect/potassium soap (especially the undersides). This removes the honeydew and kills many of the bugs directly.
-Hang up yellow sticky traps (for whiteflies/aphids) and blue sticky traps if you suspect thrips.
- Quickly check what it is: tap the plant – do small white moths fly up? → Whitefly. Are there soft green/black colonies on the tips of the shoots? → Aphids. Silvery speckles + black droppings and slender “sticks”? → Thrips.