Lies
Eurydice knew better than most how easy it was to lie, and how easy it was to get away with one. She'd found that out the hard way through the people that came and went in her life, a parade of men and women that promised food and shelter only to conveniently have nothing to spare when they came into means.
If the Fates were feeling particularly cruel, they'd take what little she had and leave her to dry. Eurydice had soon learned not to mention how much food she'd saved up.
Still, she couldn't blame them, with the weather as it was. Everyone was hungry and out for themselves, but it didn't mean betrayal didn't hurt. The worst instances were when Eurydice dared to open up to others, offering fragile trust only for them to cast her aside, content in the ways of selfishness.
By the time she met Orpheus she knew all sorts of liars and players both, and could scarcely believe that he wasn't more of the same—but his song of spring dispelled all doubts. If nothing else, she could tell he'd never lie to her.