This just makes me sad. Why would it matter how many people she has had sex with before you? Why would it matter that some of her encounters were threesomes?
Your usage of the word "cum-bucket" is also very degrading. (I know you said you didn't want to use it, but cleraly that is what you are thinking). She is allowed to like casual sex with whomever she pleases. If she has done this in a safe environment and protected herself, what is the problem?
Even if someone has had many encounters and used sex as a recreational activity that doesn't automatically mean they're easy and will immediately cheat in a relationsip.
If she is interested in you in more than a friendly/casual way and she is a decent human being otherwise, she'll be faithful.
This thread just reeks of "Women are sluts when they have had many partners and are not wife material, whereas men are awesome if they've fucked many girls!"