It sounds to me like she's testing you, i.e. trying to see how you'll react and whether or not you can handle her. The trick is not to give her what she wants if she's a masochist as this would be a reward. If you have calmly reminded her not to interrupt while you're speaking and it happens again, this may be the perfect opportunity to introduce her to speech restriction where she may not speak at all to anyone until spoken to for several hours. If she fails to comply with this exercise in self-restraint, physical means may be necessary, such as a gag. If her speech is disrespectful, wash her mouth out with dish soap or have her hold a bar of soap in her mouth for a period of time.
If you wish her to be more feminine, engage her in conversations about the kind of women you admire and why. Have her read a book on etiquette. She may not feel that she is capable of being a girly girl, or she may feel like you don't like her for who she is. You can overcome these barriers to change with good communication, trust, and encouragement rather than criticism.