Why is he coming if I didn't invite him to dinner?

Just say, “Not this time.” Let’s pick another event he will enjoy.” And then pick another event.

How about something as simple and clear as “I wanted a girls night out for my birthday. I’d love to meet him soon though. How about you guys come over for dinner/join me at the ballgame/have a drink/etc next week?”
It’s not offensive, and a friend, even a slightly dense one, will get it.

What they ^^ said.

I agree with @Likeradar. If she is such a good friend, you ought to be able to say to her, “This is an evening I want to spend with close friends and not a good time to be meeting someone new.” Anyone should be able to get the idea that you feel freer to relax with old friends than with strangers and that on your own special occasion you want to relax.

If this friend doesn’t understand, or puts her new boyfriend ahead of your feelings, perhaps she’s not such a close friend after all.

[Edit] P.S. If you say nothing and let this person bring her date, you risk bad feelings with the one who was sensitive enough to ask and respectful of your wishes. How’s she going to feel when this other one shows up with a new guy? I know which one I’d rather risk offending.

I concur with the above.

Hear, hear.

I definitely think you should draw the line. I would think you could also say something like, “This is my birthday dinner, and I wanted it to be a Girls’ Night Out.” Thus, gently, reminding her of the purpose of the event.

Or….you could just let him come and feel like the forth wheel that he’ll be…..(Wait…four wheels is good…well you know what I mean!)

Jeruba made a good point. the other friend might be bothered that she was thoughtful enough to ask and was turned down, and yet this pushy friend gets to bring her SO.

I think a great way to bring this up at this point would be “You know, Mary asked me if she could bring John and i told her i would prefer she not bring him because i want a girls night out. It wouldn’t be right for you to bring Dave since I told Mary it was Girls’ Night. So let’s stick with the original plan, keep it Girls’ Night and do something with the guys another time.”

Please post update as to how you chose to handle and how she takes it.

And maybe it is not he is coming, maybe it is he is dragged along by his girlfriend.
If you are going to talk to your girlfriend about this self-invitation of her, you could hint that the boy might not even like the prospect of being taken to an GNO?
It would turn a GNO in a GNOWOG…

@jca is right: Mary has provided you with an excellent way to bring this up and make the point.

If she says she just won’t come without Dave, here’s your answer (straight out of Miss Manners): “We’ll really miss you.”

@jca and @Jeruba….Best advice!

Be honest…its your birthday!

What I wrote:

I’m really looking forward to meeting [your new fella], but I was hoping to keep this particular dinner small and intimate, with my really close friends. Why don’t we all plan to do something inexpensive and fun in Manhattan that you know he likes to do, or go bowling in a couple of weeks at Brooklyn Bowl?

Her reply:

OK. See you Thursday. What time are we meeting at your place?

So all’s well that ends well.

It’s just one of those lessons, where, like I mentioned in another question, I am learning it’s OK to assert what I want without fear of “hurting someone’s feelings”. Either I’m not going to hurt their feelings like I think I will, so don’t take it personally, or I learn that they are people whose behaviour I must remember to not take personally.

Also, she’s so happy that she’s got this guy and she wants all her friends to meet him so badly that I think she’s momentarily taken leave of her senses. She talks about him all. the. time.

Thanks, gals! And guy!

Well well done, april!

@aprilsimnel See, no need to worry! Glad it turned out well.

Oh, she said “I”, not “we”.

@aprilsimnel Perfect!! Yes, new love can cause people to take leave of their senses and do things they wouldn’t normally do, like buying a Mower Shop….

Hurray @aprilsimnel and Happy Birthday

I’m glad that worked out for the best :) Happy Birthday!

I’m with others in saying it shouldn’t be any big deal to say you want your b-day fun to be a girl’s event this time. I doubt your friend’s bf will take it badly if his gf/your friend tells him the plans have changed.

@Jeruba: i used to always look to Miss Manners for advice. She seems to have every situation covered!

Happy Birthday, @aprilsimnel !!

I was a heartbeat away from putting my 2-cents worth and low and behold, I read the ‘I versus we’.

@jca and @Jeruba nailed it. My advice would have had only one other thing. I would have opened with a hat-in-hand apology for not having made my feelings known when it first came up. But, it all worked out…and, I think that’s what jellies like to hear.

Happy Birthday.

Happy Birthday @aprilsimnel!

This little problem seems to be happily sorted out now but another aspect no one mentioned is that it would have been extremely unfair for the new boyfriend to be in the unwitting position of unwanted guest, extremely uncomfortable and embarrassing I would think, not a great way to meet people for the first time…