Should I be upset?

My boyfriend has this friend that’s a girl which is perfectly fine with me. I’ve never met her! But when she found out we were dating she started texting him saying “I see why you haven’t checked on me in awhile now” & he was telling me now that him & I are together she comments hearts and stuff on his pictures on Facebook. He said she does that out of disrespect because she’s “jealous” & she thinks she should be the most important girl in his life although they have never been together! Just friends. But I notice when she comments hearts etc he will react to them with a heart or the new heart emoji on Facebook & now I’m thinking that if he has such a problem with her commenting those things on his post then why would he react to each one of them? Like the more he reacts the more she will think it’s okay. It’s starting to bother me, but I don’t know if I should let it? We have been together for almost a year & we have a baby on the way.