Help! Is it weird to message my manger?

So I have a very friendly relationship with my manager as does everyone else at work and we spend every shift laughing and joking. Yesterday she was leaving before us and I said I’d miss her as I won’t be working until next Saturday, she said I have her number and I can message her.

I responded with “what just message u and say ‘hey girl I miss u” and she genuinely seriously said yes. Now, I really want to message her as I genuinely do miss her and want to see how she is as i know she wasn’t feeling well last shift but I’m unsure.

One friend of mine has said it would be strange and said not to do it and two others have said to do it.

I don’t want to make anything weird or cross any boundaries but I also don’t want to not message her and for that to come across as rude but I’m also slightly scared she may have not been completely serious and didn’t mean for me to message even though I’m 99% sure she did.

It also doesn’t help that I requested her on social media not long ago and she’s not accepted it since; this wasn’t exactly a weird or inappropriate thing for me to do as she follows everyone from work and visa versa but this is the reason one of my friends says to not message her.