How can you tell someone that you strongly disagree w/ their decisions/actions w/o saying "You're so stupid!" And w/o hurting their feelings, but still getting your point across?

My best friend lacks the ability to use the common sense that God gave her. She has a child that she needs to make him her number 1 priority, but she's too selfish to do so. She's too concerned about having a man in her life and having a social life, than being worried about whether or not her son is potty-trained or if he can speak clearly. She's so pressed about dating someone that she dates people that she works with... this is a big no-no. When you're in high school and you don't know better and you have no real responsibilities, then ok, I'll permit it. But you're grown! And you have a lot of responibilities that you have been neglecting and putting off to the back burner long enough. I talk about with my husband, with my mother, and I take their advice, yet I still get no where with this girl.

Sometimes I think that I care more about the well-being of her son than she does. And that should never be the case. It's hard to talk to her b/c she's so defensive and although she hears what you're saying to her, she doesn't listen b/c she's thinking about what to say as soon as I pause to take a breath... how can she defend herself. So I opt to emailing her my thoughts. That way she will read all of it (and hopefully I won't forget any of my opinions) before she has a chance to respond. Most times her reply is "I know, I plan to do...." And she really puts forth an effort for like a week, and then it's back to the drawing board. My husband tells me to be nice when I right these emails, but that's not me. But I listened anyway.. all but once. And when I didn't listen, I hurt her feelings and made her cry. That wasn't my intentions, but she really needs to open her eyes to things. I was also told to back away and let her handling things on my own, but my Godson is at stake and I can't do that. I may not care about a lot of people, but I do care about my baby!

I need help getting into her thick skull! If anyone has any suggestions to how to talk to this chick.... PLEASE help! I can't go too much into detail about her situation, I'd hate to put her out there like that, but if you feel where I'm coming from a little bit, please tell me what you think....