It is highly possible that I am the worst mother alive

I am sitting in bed, listening to Emily scream her head off.
She is with Matt, but is throwing a huge, ginormous fit.
I honestly don't know what to do.
You see, she still nurses. Yes, yes, I do know she will be 3 in March. And yes, I know there is going to be a new baby in a matter of weeks. I know all of this.
To wean or not to wean has been the ongoing question here.
On the one hand it would be really great for her to be weaned before the baby is born.
On the other hand, I do not want her to feel rejected by me. And I really don't want her to hate Natalie.
It is such a hard, hard decision. She really enjoys nursing. And I really do not at this point.
So tonight, I let her nurse to sleep, which is about the only time she nurses. But she woke up after about an hour. And not just a little. She must have dreamt something bad because she woke up nearly screaming. So, I scooped her up, and naturally, she wanted to nurse. Normally, she will latch on and nurse for just a few minutes and I can tell her that's enough and she's fine with that. Not tonight though. She just wanted to nurse and nurse. And I just wanted to crawl out of my skin. I'm reading a book about tandem nursing, and it turns out this is a totally normal feeling when you are nursing while pregnant.
I told her that was enough, and she lost it. And she's been screaming ever since. And it's breaking my heart. I'm not sure what we are trying to accomplish here. All I know is I don't want to nurse her right now.
How selfish. She needs comfort and all I care about is my own comfort.
See. I told you..worst mother alive.
This all sucks. Really, really bad. My mother would tell me that she has told me all along to wean her, we have just really struggled with if that was the best thing for her. It's funny, because my mom likes to spout off about me weaning her, she has no idea what we have been going through regarding the whole weaning issue. It isn't one we are taking lightly, it has been a source of major stress for us for some time. It's hard to know what the right decisions are when it comes to our babies!
I need a fairy godmother to come wave a wand and make this all better. *sigh*