Is she in the wrong or is the girlfriend a bit possessive?

A girl was once classmates with her now professor and they were friends. He’s older than her by a few years. She’s like in her early 20s and he’s in his 30s

he enters into a relationship and bc she’s really cool with the guy she follows his girlfriend as well.

They were both sick from Covid and she commented “feel better” under his or her post (not sure)

He then tells her that his girlfriend got really upset about it …

Is she in the wrong or is the girlfriend a bit possessive?
Post Opinion