Okay, I'll bite
1) Mrs. Trump has been a US citizen for only 10 years. I will cut her a little slack in the US Flag Code for civilians. Is the First Lady a "civilian"? I dunno. Probably. I'm not going to judge. When in doubt, stand at attention. Which she is doing.
2) President Trump is Commander-in-Chief of all US military. Military salute is in order. Civilian FLAG CODE does not apply to non-civilians.
Commander-in-chief of the US military is still a civilian. this was by design. Presidents saluting the military in return is fairly new (around Reagan). I dont have context for the photo tho, are they standing for the flag, or military on parade as they pass by?