She does it everyday

Hello,

I am in a current situation where my boyfriends best friend who is a girl keeps texting him and I believe that is okay because I have guy friends that I text as well, but not every single day. Let's refer to her as "Brianna." I have met Brianna and we get along really well and I love her because she is the sweetest thing and we texted each other once in a while too, but she is texting my boyfriend everyday, and the twist here is that she is married. She will sometimes text him saying that she misses him and that's okay because one of my guy friends and I will say that, but we only see each other 1 time every 3 months because of distance and we only talk 1 time every 2 weeks.

What I am getting at is that Brianna sees my boyfriend or hangouts with us and her husband every 2 days and she still says that. It honestly never bothered me until the other day when she left for a vacation with her family and on the third day of departure she texted him saying "I miss you." My boyfriend told me and I was asking when she was back because I missed hanging around with Brianna and her husband as well. The following day she texted to same thing, but said it 3 times during the whole day to start a new conversation with him. One saying, "I'm bored and miss you."

In my defense I feel like it is okay to say I miss you to someone, but isn't there a limit to saying it? Especially if Brianna is currently on vacation with her husband and family. Shouldn't she be enjoying herself and not texting my boyfriend all the time?

I may be overthinking this, but I did speak to my boyfriend about it and he does agree that it is over the top and told me that he would not like it if my guy friends did the same. He also said he will talk to her about it, but I also told him that I don't want any conflict because I don't have anything against her...
My question is: what do you think? Am I overthinking this situation?

You're fine, I think its perfectly reasonable for a person to think that way in regards to that.
You aren't overreacting in any way, you're just showing concern. Which is what needs to be done, you're communicating like you're supposed to.
When people don't communicate, it creates unhealthy relationships and unnecessary drama.

You did good. You mentioning how he would feel if the script was flipped is totally true.

You are not overthinking. She should not be texting anybody's boyfriend constantly saying i miss you. It is not acceptable. If you continue to let this situation persist she will steal your boyfriend.