Not overreacting. What a self-centered witch!
I like this. Short, accurate, and to the point.
Nemesis, I'm glad that you are home and you and your baby will remain in my prayers.
I think that your proposed answer is way, way too nice. This woman is also not really your friend. Considering her callous treatment of you and your condition, I think that there is something seriously wrong with her.
Don't just tell her that your health precludes your attendance at the party. She will then make plans to drop off the dang catalog so that you won't be left out of the **fun** - aka $sales$.
I rather like Judah's suggestion of "letting her have it. I wouldn't send her a text or email. I would wait until she contacted me again about the party, then I'd let her have it. Not rudely, but angrily. Does she not realize how precarious your situation is to have been put on bed rest! And she wants you to risk your health and that of your child to attend a sales party! And she lied to you about it! I'm furious on your behalf.
I'm furious on your behalf, also. If you aren't up to the anger and vehemence that Judah suggests, perhaps you could just tell her quietly that you are totally shocked that she would insist that you come to a sales party when you are on bed rest to protect your baby. You could tell her that you want to take a break from your friendship with her for awhile, because her behavior is so upsetting to you.