Search Results: liking a girl with a boyfriend

Me and my boyfriend been together for 1 year and 3 months
He post gym selfies of himself and post them up on his facebook and instagram
He also post pictures of us on his facebook and instagram and put captions like "with my pretty girl" and "with my other half"
So anyway, he works in a nursing home so there are a lot of females that works in his workplace but most of them are older
There are few younger ones and thats what I wanted to talk about now
There are 2 girls that works with him on his facebook and instagram
He talks to them at work
And I've noticed that every picture he uploads of himself on his facebook and instagram, they would "like" his photos but no comments
And when he uploads pictures of both of us, they would "like" the photos only as well
Should I be worried about this?
Are they interested in my boyfriend?
Or it doesn't mean anything other than just liking the pictures?
I see that he does like some of their pictures as well

So few months ago, my boyfriend told me about this girl at his work.
He told me that she got dumped by her boyfriend (of 8 years)
Anyway, so a week later, we bumped into her at the mall and he introduced us.
She already knows im his girlfriend
She would be like "how are u? Nice to meet u"
But anyway, everyone at his workplace knows im his girlfriend since he always post pictures of us on his facebook and instagram and puts on public
And he put captions like "with my pretty girl" and "my other half"
He even invited me to his co-workers dinner party last week and never left my side - he kept hugging me and putting his arm around me, etc
She wasn't there but we all took photos together and in every photo, he would always be beside me and close to me
The girls that took the photos put the photos on facebook and obviously that girl seen it cos she liked the photos
So anyway, that same girl that got dumped by her boyfriend... recently she has been liking all my boyfriend's photos
Everytime he uploads a new photo of himself, she likes it
On facebook and instagram
But she does also always like our photos (me and my bf)
I can't access her instagram cos its on private but i can see some pictures on her facebook
He likes few pictures of hers as well on facebook
I confronted him and he said "so what? she's a friend at work. I like all my friends photos. Even the ladies that are married. Even the guys at work. Its just a like. We dont talk outside work"
Is she interested?
Is he interested?
Or am i overthinking it?