To Spray or Not to Spray

[Melody]

Okay, so I have been taking care of my mother's orchids for a bit. She's out of town for a week. She has been gone a few days and her orchids have stupidly been with mine. Today I noticed mealies on 2 of her plants! I sprayed the two with Orthonex (systemic) and quarantined them ...but I'm worried about mine. Should I just assume that hers infected mine and spray them as well? Or wait until I see a visible sign? One or two of my plants may in fact have been touching the infected ones. I'm worried.

And I'm kicking myself for not checking over hers before letting them near mine... I just assumed she would have told me of any problems, so I am guessing she didn't know about the outbreak...I don't think she pays attention. *sigh