If you want to be more neutral:
* "Someone who embellishes the truth" - This suggests exaggeration rather than outright deception.
* "Someone who has a different perspective on the events" - This implies disagreement rather than dishonesty.
* "Someone who's prone to misremembering details" - This softens the blow by attributing the falsehoods to memory issues.
If you want to be more critical, but less harsh:
* "Someone who isn't always truthful" - This avoids directly calling them a liar but implies a pattern of dishonesty.
* "Someone who lacks integrity" - This focuses on the character flaw rather than the specific act of lying.
* "Someone who's not entirely trustworthy" - This hints at the person's unreliability without directly accusing them of lying.
Important note: It's crucial to consider the context and your audience when choosing a euphemism. In some situations, it might be better to be direct and call a liar a liar.