"Help me stop myself from doing something regrettable."
You have proposed a paradox. It's a catch 22 you will regret it either way but you are using us as a proxy to avoid the inevitable pain of the situation by puttin the responsibility into somone elses hands to decide for you.
If you want to wish her happy birthday do it. If you don't think you will be able to stop yourself from unleashing your pain an frustration in your communications then don't. In any case explore and experience these overwhelming emotions.
I agree. Feel the Emotions whatever the decision rather than hide from them (this came from family of origin). I dated a Borderline cause I ran from emotions. Who better to date than a highly emotional person when I feared them. My ex made it up for the both of us.
And really ask yourself what it means if you do. What are you hoping to gain?
Find your reasons as to why you're attached rather than feverishly protecting NC.
I agree with these 2 posts 1,000,000%.
Go ahead, wish her a happy birthday and resume NC. Don't expect a reply or anything else.
or
Stay NC.
You see, it really doesn't matter if you plan on immediately resuming NC. It's all how you think it will affect you. I sent my ex a birthday card with no return address, I texted her happy Thanksgiving, and I bought that cheating, lying, hypocrite Christian a nice new bible for Christmas. Other than that, I have been NC(except the 1st month out). I did all of that without ever seeing her or actually talking to her.
On the other hand, I haven't heard from her at all. Not one time. And I'll bet you $100 right now that I won't even get a "Happy Birthday" in April. And that's OK, I don't expect schit from her.