Co worker acts weird around his girlfriend? but only towards me?

I have this one co worker who trained me at my job , he was nice (he’s a middle eastern guy) he was so sweet to me during training and even after. I notice the day after he was training me his girlfriend who also works on the floor came in the next day and was like “girlll he was at home telling me he’s a better trainer than me “ then proceeded to ask “who was better and who was more fun me or him “ mind you her boyfriend who trained me is like 20 and she’s like 25 (and I am 22 F) 😭😭 and oh it didn’t end there because they both Went on break and when they got back his girlfriend also said to me “girrrrllllll somebody told me you were scared to do acuchecks “ and I’m just in my head like WHERE IS ALL OF THIS COMING FROM? I have repeatedly caught him staring at me when I would come out of a patients room , while I’m walking , or while I’m talking to other co workers he will stare but when his girl is at work HE AVOIDS ME AT ALL COSTS, he won’t look and won’t even say anything … like what’s going on? His girlfriend even called me beautiful yesterday and she does the same , she tries so hard not to talk to me when he’s around …… like? ITS ITS BEEN A CONSTANT THING FOR MONTHS & I really don’t get why they both do that and then when one of the other is gone they are more open to talk to me and nice..
Updates
10 mo
I even noticed he would have a normal conversation with the rest of my co workers but acts even scared to talk when his girl is there , it’s weird
Co worker acts weird around his girlfriend? but only towards me?
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