Why would our employer act this way?

Since a year now, this guy who is a manager, complained that a girl, we'll call her girl A, does not like him. Girl A treats him indifferently.

At the same time the guy was, and has becoming closer to someone we'll call girl B; who has always been in love with him. This guy and girl B having a relationship now. It seems like they are hiding some of it.
Girl B thinks girl A like the guy, and flaunts her closeness with the guy. But when girl A first met him, she had already mentioned that he is unattractive to hrr, despite everyone swooning over him.
Girl B kept telling girl A about how she feels about getting him. Girl A was and has been indifferent to the situation. But Girl B acted threatened that the guy will like Girl A. Especially because he kept tslking to everyone sbout girl A not liking him, even though he helps her.
The guy flirts with girl B all the time. He is trying to hide from girl A as to how strong the relationship has gotten with girl B. The guy is now talking to girl A in a rude way, since she seems aloof of the entire situation. And is becoming more upset when he thinks girl A has a boyfriend and is textibg a guy (s). Even though there was never any interest in him by her.
If anyone, especially girl B, is seen texting, which they do a lot; he allows it and does NOT repremand them. If he sees girl A glancing on her phone (that's charging, he throws a fit, and screams her name at her.
Its allowed to be on phone out of site of customers.
He is the supervisor of both of them.
It appears that its allowed for anyone
To date each other.
Not a sexual harrassment situation.

The guy and girl A ARE the ONLY two people at work that avoid each other and are not talking directly to each other. Every time there is an issue (guest related or work related) and girl A is telling another manager or a coworker, depending on who needs to know; if the guy is looking nearby, he goes up to that person to ask what she said after she walks away. Never directly asking her. He even talks to her through others and vice versa. So its obvious something is up.

He ALWAYS try to go out of sight when girl A comes to work. Not just in his office. And find a corner to stare at her as well. When she passes by him, he stands real quick to the side the exact way a solder does when his general walks in. Except he clasp both hands together over his crotch instead of a salute. No joke. He tries to schedule his shifts where he has less interactions with her. Like coming in earlier to leave earlier before her shift starts. Or scheduling his days off when she is schedule to work.

On New Years eve, he was all into Girls A's face, chumming uo to her. Calling her early. Girl B kept running up to him to try and talk to him. Then he would walk off when gurl A comes near. At one point him and girl A was talking a lot, even laughing together. Then at some point you could see them go back to avoidinvpg each other. They started talking again towards the end of the shift. Theb when she was leaving, he said nothing to her just ignored as she went near him to leave. He wished eveyone a happy new year except her. She left him at work. Watching them looks bitter sweet.

Any ideas what could be really going on with them?