Is it acceptable for my boyfriend to invite a female friend as his plus one to a work Christmas party that we both attend? I’m 35, and he’s 34.

My boyfriend and I have been officially dating for four months, though we've been involved longer than that. The main challenge in our relationship stems from his many female friends—some of whom I know and some he claims I don’t, simply because the topic hasn't come up. I feel that in a committed relationship, it’s concerning for my partner to have an abundance of female friends with whom he texts, FaceTimes, and spends time privately. He disagrees, insisting he should be free to be friends with whomever he chooses. I'm not saying he can't have those friendships; I just find it troubling and worry it could lead to misunderstandings or unwanted feelings. We both work together and are attending our office Christmas party, where we’re allowed to bring a plus one. He mentioned it would be fine to bring a female friend, and I find that disrespectful and inappropriate. When I shared my feelings with him, he asked how that could be disrespectful and pointed out that I seem overly concerned with what others think, calling me insecure and childish. I struggled to articulate why it bothers me so much. Ultimately, I asked if he could give me a heads-up about whether he planned to bring a female friend. He responded by saying, "Why should I have to tell you? Why does it matter? I can bring whoever I want." What do you think about this situation?