Dr. Ellis Grey taught her daughter to always tell the truth.
Of course, Meredith went years without knowing she had a sister, but thats neither here nor there.
The truth is important.

Credit: Rick Rowell/ABC
The truth is a vital quality we should protect.
The truth sets you free!
Take Meredith for instance.
Thats right, people.
Meredith Grey is ready to mingle.
Look alive, men of Seattle.
Shes giving you thirty minutes to woo her into submission before she heads back to the OR.
On your marks, get set, date!
Meredith is going old school.
She knows nothing about her guy, other than the fact that is name is Ted Mosby John.
Hes totally in second place on my official Meredith Boyfriend Wish List right afterScott Speedman.
#BenCovington4ever
John is a software guy who appreciates that Meredith is a big deal in her field.
Thats what we call a green light in the dating world.
Meredith is having a good time.
Especially when she bonds with Johns the one thing theory.
Picture it: The date is going great.
She seems to like him.
Fireworks are poised for explosions.
Then she says the one thing that makes it all go south.
Or confuses theyre, there, and their.
Whatever the case, the one thing ruins it.
Meredith finds this delightful and entirely true.
Then she notices Johns facial expression change from pleasant to horrified.
Then they leave the restaurant to get to know one another even better.
He has the resources to secure a flexible schedule.
He has no kids and thinks that single moms appear desperate.
Aaannnndddd theres the one thing.
Meredith bids John adieu and walks away.
The truth has just set her free.
It can be interpreted in many different ways.
Especially if youre the chief.
Station 19(shout out to the crossover!)
firefighters bring in an unconscious woman and a young man who is having trouble breathing.
Karev learns that the guy has a lung condition known as a pulmonary bleb.
Its a pre-existing condition.
His mom will freak out.
And if Karev performs the surgery, he will sue.
Karev is irritated by all of the rules, so he goes to Webber for counsel.
Webber cant stand that Karev is clearly unable to shoulder the load of the chief.
So Karev stabs the guy with a scalpel and I have Izzy flashbacks.
What in the world?
(Wink, wink.)
Be gone, bleb!
So long, truth!
She knows Betty came home high and she knows Betty is lying about it.
His mother was a drill sergeant full of rules.
Amelia calls Owens mother and asks her what to do about Betty.
Amelia has to give her the tools she needs to make it back safely.
Betty freaks out like any teenager would and Amelia smiles, knowing that shes got this.
Its also a way for Miller to stalk Maggie.
Lets add that random log to the Jackson drama.
Unfortunately, Natalies heart is too damaged to repair.
But he insists on assuring Max that his mother is going to be okay.
Maggie is tired of dealing with stupid people.
Amelia thinks that doctors should always stick to the oath.
Then he runs off to discipline Betty.
She rants to Meredith about how surprises are unfair.
Max needs to know his mom is probably going to die.
Jackson needs to tell her before he goes off to take random pictures of trees.
And Amelia…
Maggie looks at Meredith.
Meredith raises her brows.
Maggie breaks the Hippocratic oath by telling her sister that Teddy is pregnant with Owens baby.
How do you like that truth bomb?