Lets first start off with the definition of trust.
trust : assured reliance on the character, ability, strength, or truth of someone or something
I once heard it explained this way. Trust is knowing that some one will react the same way to the same situations. Think about that and the people who you trust you will find its true. You don't trust the people who fly off the handle or act erratic, repeatability builds trust.
Now, holding all this in thought lets return to the topic of trusting a woman.
Trust her to be nosy. She doesn't come over to clean your place because she wants to. Cleaning is an excuse to rummage through any bills, bank statements, old love letters, receipts or black books. Assume anything that is not under lock and key will be read, and don't leave the key out in the open for the "cleaning" lady to find.
Trust her to be Jealous. Jealous of everything, your sister, your mom, your car; anything that takes time away from you being with her. Expect to catch crap even if its her own vehicle.
Trust her to be insecure. The little voice in her head is constantly yelling at her that "your boobs are too small", "your ass is huge", "fat...ugly....bloated...". With all of that being blasted between their ears I'm surprised they have enough confidence to get out of bed in the morning.
Trust her that Given an Inch she will take a Mile. What starts out as lipstick in the bathroom drawer, quickly escalates to tampons under the sink, and having her moving in by the end of the week. Oh, and don't think about taking this stuff back to her, she will interpret it as you not wanting her stuff around. Which, (see above about the little voice) she will tell her self that you don't want her around and all hell will break loose.
Trust her to mark her Territory. Just so we are clear, you are her territory and so is your place. Ever notice, every time she comes over something is "Accidentally " left at your place. Notice how its always something gender specific, the lacy thong, the gold hoop earrings or the red high heels. Its never anything that could be easily explained away should another female show up. Ever wonder why she makes you hold her purse? Know you know.
Trust her to Spend money. More specifically, expect her to spend your money. She will view any positive balance as spendable and then create ways to spend it. Its best to have the woman believe that you live pay check to paycheck and own nothing but the shirt on your back.
-Mr. WAM