Tip / Tips

Are these correct? If not, why?

Scenario: She's a waitress at a restaurant and I'm talking about her.

1. She gets so much tip. (Is this correct?)
2. She gets so much tips. (If this is correct, why? I do hear people say
this a lot? Is that how you spell 'tips' ?)

3. She gets so many tip. (This sentence is incorrect?)

4. She gets so many tips. (This sentence is correct? But I shouldn't use
this one?)

5. She gets a lot of tips. (If this is okay, how come #4 is not
often used?)
6. She gets a lot of tip. (Is this okay? I don't hear this a lot?)

Which one should I use? What would you use?

Thanks.