E.P.
Keep working with her - I remember some previous questions about this little one. It sounds like she is making some headway with manners. She needs role playing and guidance and, unfortunately, if you are the only one giving it to her, it makes your job harder. She has learned how to have bad manners and can learn how to have good manners. She may truly have a hard time dealing with other kids if she is not the kind of child who has been exposed to a lot of kids or who has grown to be manipulative to get attention (i.e. pouts, lied to an adult, etc....). Talk to her when you are not in the heat of the moment. Role play with her with stuffed animals or toys. Sometimes, when children are nervous, they respond the exact opposite of what you'd expect. Making comments about "sex" or "bras" may be acting out or may just be to get a rise out of kids. You may have to give more detailed advise on how to be a friend - one lesson at a time.
Don't make excuses for her (i.e. "I'm embarrassed for her....".) Don't tolerate bad behavior, however, make sure you are praising her when she does use the right words, right manners, etc... Don't be worried that your child is NOT mannerly - kids change. She can learn. Little steps. I think it's good to be present for play dates but, you can't always intervene for her - or hover. You have to arm her, in advance, with how to resolve conflicts (i.e. "two-choice rule", "rock/paper/scissors", "eenie-meenie-minie-mo", or whatever.....). Role playing will help. Unless there is a big conflict, you'll have to trust that she can figure out how to resolve it and what behavior doesn't make for a good resolution (i.e. pouting, yelling, bossing). She won't learn without making mistakes. Teach her to be the "world's best negotiator" - even calling her that when she succeeds. When she learns this - she will gain confidence. It's not realistic to think that all play dates will be at your home. When you trust that she is doing better, just make those play dates shorter at the beginning.
Don't worry about what other moms are saying - nobody's child is perfect - in fact, being a parent can be quite humbling. If those moms are whispering about YOU.... that's bad manners! Shame on them!
Keep up the good work. This child needs you!