Lies crop up every once in a while in even the closest of friendships and relationships. Certain lies, however, such as those people use to hide acts of infidelity, can strain the relationship over time -- especially when the truth comes out. If you fear that a female friend of yours isn't being entirely truthful, you don't need a lie detector test to judge her honesty. Several signs exist that you can look for when trying to spot a liar.

When a girl is lying to you, she will try to keep her fibs as simple as possible, suggests psychology professor Edward Geiselman in the Science Daily article, "How to Tell When Someone's Lying: Psychologist Helps Law Enforcement Agencies Tell Truth from Deception." For example, when you ask what she and her friend did last night, she might simply answer, "We hung out." When pressed for more details, she might repeat your question or pause before answering. Also, look for inconsistencies in her rate of speech. She might slow down to think of a lie, and then speed up suddenly when she becomes aware of how slowly she is talking.

A girl who is fibbing will tend to "self-groom" while speaking, says Geiselman. For example, she might play with her hair or pick at her fingernails. Liars also tend to direct hand gestures toward themselves, rather than outward. Because she might be worried about being detected, she might also limit her use of gestures. If a girl who usually talks with her hands keeps them abnormally still during conversation, this is an indication that she is hiding something and afraid that you might catch on.

A girl's choice of words can also reveal if she's lying, suggests psychology professor James Pennebaker as cited by Rachel Adelson in her American Psychological Association article, "Detecting Deception." Pennebaker and his associates developed and utilized computer software to help detect when people lie. Based on the results of their work, specific markers were discovered that indicate probable lying. For example, lying women tend to steer clear of first-person pronouns, which allows them to create psychological distance between themselves and the fib. For example, instead of saying, "I found this necklace in the park," she might say, "Someone left this necklace on the ground."

Her mouth movements can reveal if your female friend is lying, says communication instructor and body language expert Patti Wood in her article, "How to Spot a Liar." When lying, the mouth shows signs of stress, as if trying to hold back true details. For example, she might purse her lips or suck them partially inward to avoid any potential, tell-tale clues her mouth might give, such as sadness or a smile, or other unconscious movements. In addition, nervousness tends to dry out the mouth, so she might also lick her lips more than usual.