What’s the proper way to correct someone when not saluting an officer?

You could have asked soldier if they noticed the officer's that she just past. Then again was you in a no solute area?

Praise in public, correct in private. It is one of the duties of leadership to teach juniors. One on one where possible is best

You weren't aggressive.
Aggressive: " Hey!! Sh*t for brains!! Did you not see these two SUPERIOR OFFICERS
(Capitalization denotes speaking at a perceived auditory decibel range akin to the noise level present at the detonation of a 10 kiloton nuclear warhead)!!
Now drop and shove the f*ckin' Earth off its normal orbital path until we are over your perceived horizon!!"

Non-Aggressive:
"Do enlisted soldiers not salute officers anymore?"

Pull the soldier off to the side and remind them of customs and courtesies. Holding the standard is what makes us military personnel and keeping that state of mind. The more you let lower personnel to lose their grip the worse it is going to get when eventually someone will say what is the big deal.

My first question would be WHAT THE FUCK IS YOUR MAJOR MALFUNCTION? You do realize that was two officers that passed you without you rendering the proper respect and saluting them? The only way I would say nothing is if it was an officer that passed. A PFC has no reason or right not to salute his/her superior officer.

There is no other way.

F that agressive BS. Drop the PFC for push ups and maybe put her on KP for about a week

Happened to me ages ago. I apologized for not saluting to the Commissioned Officer, while saluting. The E-7 that was with her asked if I was okay (I was on a pain pill that messed with my vision so badly I was looking at the ground). I said that was no excuse, and the E-7 said words to me I hear to this day: "Stay alert, stay alive soldier".

Should have just lit her ass up. Sometimes that's just what everyone needs.

I find the best way to start those conversations is with a "Hey Motherf***er" and go from there.