Only in a very dysfunctional and immature relationship.
Would a woman say she had sex with another man only because her boyfriend didn't believe her when she said nothing happened?
Stranger things have happened!
If a man accuses his wife/ girlfriend for having sex with another man yes she has every right to give him a taste of his accusations yes sure i may be wrong but she should give him a taste of his own medicine. If a woman/ girl says she didn't have sex with a certain man i would want give her the benefit of the doubt and believe her i wouldn't want to falsely accuse her of doing something that she didn't do cause that would just be wrong.