Reading the rules of Yula's Close Combat Bar I don't know if I understood right:

" Once per activation ..." What does it mean?

Yula may make a melee attack each time a character pass in a circle adjacent her (but only once for each activation of a specific character).

Example: During McNeal's activation, he pass in a circle adjacent Yula and she makes the melee attack given by the Close Combat Bar (like an overwatch). Mc Neal goes on with his movement, after that (during the same McNeal's activation) he come back on your feet and pass another time in a circle adjacent Yula, but she doesn't make another attack becouse she can use Close Combat Bar once per activation.

During the same turn (after next Reich's activation), Union activates Commando Alpha. He moves in a circle adjacent Yula, and yula may attack him... becouse this is another character's activation.

Is it correct?

Hi

yes, you´re right - once per activation of the active character may Yula make one overwatch attack against him if he´s (the active character) in a circle next to her.