Regarding your need for honesty, make sure you clarify what that means to you. "We need honesty" is fine to say, but honesty is a wishy-washy term. It means different things to different people and in different contexts.
If she was telling a lie, then that's dishonest by just about any metric. But how do you feel about omissions? Many people don't consider omissions to be dishonest. Some people value privacy above or equal to honesty. So to that end, your need to have everything on the table may not be compatible with her need to have privacy.
Also make sure you're creating a safe space to tell the truth. She may have feared criticism for cancelling your plans. She needs to know that she can tell you the truth and even though you might be disappointed, you won't give her a hard time or try to change her mind.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker