How do you go on about trusting a woman you're being intimate with that she is in fact loyal to you?

Whenever she says she's going to a party with friends and not worry, but upon coming back to you there's instincts, suspicions, or doubts that she's doing something there that you would disapprove of, yet she says nothing happened and not to worry.

What do you do? What do you say? Do you just forget about it? What if this is a rather consistent thing?
How do you go on about trusting a woman youre being intimate with that she is in fact loyal to you?
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My take? Never trust a woman without any prior reputable history. Always test, verify, or make sure that everything she says is backed. Despite a woman being trustworthy, she is, at the end of the day human. So, if she makes a mistake, especially a significant one, she will react as most humans do and try to cover it up, divert attention away from it, be in denial about, etc.
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Some women will call you insecure or controlling, but this is to be expected of women who don't have the best of intentions for you while in a relationship or have something to hide from others. Actually, name-calling or verbally attacking someone in this way may be an indicator that they cannot defend themselves logically, so they default to emotion. Trust requires evidence
How do you go on about trusting a woman you're being intimate with that she is in fact loyal to you?
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