Tell her to maintain eye contact while you choke her.

Count down until when you're going to release her, making the number higher each time.

Once my Dom held my face into his chest to suffocate me, released, and then repeated for longer intervals each time. That was one of the most intense experiences I'd had with him, I think because it was so intimate, and he had such a high degree of control.

Another fun time was kneeling with him choking me while standing behind me.

The release and repeat is so important, and having that dominant, calm, controlled attitude. There's nothing bland about submitting and allowing someone control over your ability to breathe. It's like letting someone have control over whether you live or die.