Can fleas nest on my vagina?

Fleas are host specific parasites. They need animal blood, not human blood to survive. They often bite humans when their desired host is not around, but they will not survive for more than a day or so. I would not worry about them nesting on or in your vagina.

Fleas? No. The closest possibility is pubic lice ("crabs"), which -- as the name suggests -- can settle in the pubic area, i.e. the hairy area in the genital area. In that case, the most obvious evidence usually is itching and tiny white or grayish spots (nits, the louse's eggs) clinging to pubic hairs. If you practice genital shaving, you are at very low risk of pubic lice.