Good friends are hard to come by, but I believe parenting skills will ruin some friendships and bring together others.
I completely agree with you in the first part of your message. I'm a disciplinary parent completely overly-sensitive to how other people may react to our kids. If they start getting fussy at a restaurant, one of us will take them outside until food arrives or we'll finish-up early.
Had that been my child, I would have gotten a replacement toy - but, my kids would never have been allowed to get to that point. I often ask people if my kids are bothering them and apologize when they act their age.
If the friendship's important to you, I'd voice your concerns. She may not know or realize how distracting her child's behavior is to other people (but, it doesn't sound like she really cares either, unfortunately). The worst thing that can happen is that she chooses to end the friendship, and you're better off without a terror running through your house and influencing your children.