First of all- stop blaming yourself! Your daughter was probably like this in the womb. Smart, strong, independent, and yes...stubborn! :) I know, because my son's personality was clear even in utero, as well. All we can do is love love love our kids, give them boundaries, and just do the best we can. That's what you're doing, and you're an awesome mom!
I'm also a former elementary school teacher, and let me tell you- this is SO NORMAL for girls. This obsessive best friend thing is quite irritating for teachers and mamas, but it's completely developmentally appropriate. It's also a way of testing teacher expectations and class rules. So it's the teacher's job to do exactly what she's doing. Switch the seats, and have a plan to deal with the meltdowns that occur. And if worse comes to worse, maybe mom has to come in and observe and occasionally intervene as needed.
Your daughter is independent, and will probably not want you there! Thus, she may learn her lesson. In any case, it's very early in the year. This is the time for meltdowns. It will ease off as 2008 comes to a close.
Your daughter may enjoy spending time with her friend outside of school, but I doubt this will change her behavior at all in the classroom. And 4 years old is still too young to expect kids to do a great job at controlling jealousy and possessiveness. It's so exciting to have a real friend! It's so empowering, to feel loved by someone who isn't a family member. And just wait for the fights they'll have. The tears and drama are gut wrenching (for them). Don't give a hint of a smile, as you wipe away those tears. She'll be outraged!
And finally, the listening. That's a tough one. No four year old is a good listener. And plenty of adults aren't either, so kudos to you for beginning the listening lessons! Stay patient, and keep gently reminding her that it's your turn to speak. Or her friend's, or her sister's, etc. Ask her questions about what you said, but not in a patronizing way. Just casually, and really listen to her as well. It's easy to tune out chatty four year olds, but they're smart. They know when we're not listening, and they follow our lead.
Good luck! Sorry for the long response. Maybe I'm just missing my classroom, now that I'm a stay at home mom. :)