Some of the most interesting things in life are gross. Gross is fun, especially to kids! There are dangerous gross things, and gross things (to us adults) that are not dangerous at all.
Public bathrooms—yes, disgusting. I try to avoid them, but with small children sometimes you just can’t wait until you get home. I flat out tell my kids to not touch anything in the bathroom once they’ve washed their hands. Use some hand-sanitizer once you get out of the bathroom if she’s too little to understand and just can’t keep her hands off things.
Other nasty things, like garbage and dead critters, should also be off-limits. A small child isn’t going to understand about germs, but just keep stressing the idea that those things are “yucky.” Again, some hand sanitizer is great for when her little hands move faster than you can.
Bugs, frogs, mud, dirt, sand—no problem there. In fact, you and your child should go in search of these things on a regular basis. Let her pick up worms, and don’t freak out. Catch some frogs, catch some grasshoppers, play in the mud. Then, wash your hands. As long as your child washes her hands after exploring the dirtier side of nature, she’ll be fine. She also won’t grow up to be one of “those girls” who screams and squeals at the sight of something slimy.
Besides, exposure to germs is the only way to help build up her immune system!
I have three kids, and while certain things do really disgust me, anything that can be found in nature is OK for my kids to handle (unless it’s poisonous, of course!). Last year my daughter’s girl scout troop got to dissect squid at the aquarium, and my daughter dove right in without so much as a shudder. She’s an expert at catching snakes, frogs, and turtles, and is perfectly healthy.