not pregnancy related

This is totally not pregnancy related but I don't know where else to turn to ask for help. My cats are like my babies so I feel so bad. It's just my little cat who has fleas and it's so bad. We've given her baths with flea shampoo, we've given her liquid medicine on her neck for them, and she's currently wearing a flea collar that she's had on for about a month. And she still has them really bad. I feel so bad for her. Does anyone know how else we can get rid of them? I also should mention that they're not on my other cat. It's just her. There's so many of them every time we look. In her private area, behind her ears, in her ears... They're everywhere and it makes me feel so bad.