just to be fair heres the other side 1 - She's accusing you
"Often, when a woman accuses her mate of having romantic feelings or involvement with others, she's projecting her own feelings onto him," says Susan Heitler, Ph.D. If your girlfriend lacks trust in you, she may not trust herself.
2 - She wants more
If she's telling you she needs something else from the relationship, whether the request is for more intimacy or a stronger emotional connection, listen. "A woman really lets you know what she's thinking about," says Al Cooper, Ph.D., director of the San Jose Marital and Sexuality Centre. "If she tells you she's feeling unappreciated or unimportant, or wants more intimacy, it can be the last-ditch effort before she embarks on an affair."
3 - She's online
If you're hearing "You've got mail" more than "I love you," she may be spending time searching the Web for someone to talk to. "Even if she doesn't want to cheat, the Internet is particularly seductive for women," says Cooper. "It makes men have to talk, and women want a communicator."
4 - She's looking hotter than ever
If she's started something on the side, sudden changes in behavior or appearance (for the better) are common.
5 - She's sappier than ever
"If she's watching romantic movies and reading romantic books, the feeling she's getting from them is feeding something inside of her," says Pepper Schwartz, Ph.D., a relationship expert who's online at perfectmatch.com. If your mate's not expressing these emotions in your direction, she might be looking for a new leading man.
6 - She's more attentive to you
A study published in the Personality and Social Psychology Bulletin found that when a man's girlfriend is cheating, she'll start to make obvious attempts to increase his satisfaction in the relationship, as well as say derogatory things about her paramour. It's a misdirection ploy to lessen your suspicions.

You forgot #7-

She tells you she's cheating. Happens all the time.

This holds true for men as well....I should know

And #8....(S)he's gotten b*tchy and finding fault with everything you do.

I can vouch for this one, I've done it. I wasnt satified in my marriage anymore, so I found it elsewhere, and filed for divorce.

Easy, Ladies are pimps to

Oh, I'm not hatin'... just wondering, is monogomy overrated? Maybe there should be a 5 year contract signed in advance. When it expires...move on...no surprises that way

Definitely G2G for both genders ... except the sappy thing lol

I should have read that three years ago