She was played by Taylor Momsen in the live-action movie of the same name.
Cindy Lou was about six years old and knows the Grinch early in the story unlike her cartoon version. Thanks to her doing some investigative reporting after The Grinch save her from the posting stamp machine.
Unlike the rest of The Who's except Martha, Cindy believes that there is some good in The Grinch who's just a misunderstood creature and not mean.
Later, Augustus May Who, the Mayor of Whoville, angrily accuses her of robbing everyone when the Whos awake to their homes being ransacked by The Grinch.
However, her name is cleared shortly after her father Lou stood up for her and she later helps the Grinch return every item back to the Whos after sneaking aboard his sleigh by telling him that no one should be alone on Christmas.
In the last scene, she gave the Grinch a kiss on the cheek after telling him by wishing him a Merry Christmas, they both sang and she welcomes the Grinch and Max to her family at the end.
When Cindy Lou first met The Grinch at the post office, they didn't get along since The Grinch was bad and thought that Cindy is just like the other Whos who only care about presents.
Even though he did save her from the stamping machine, he just don't want to admit that he only did that because he care and Cindy Lou decide to asks everyone what they know about him and soon discovers that he has a sad past.
Later, Cindy Lou meets The Grinch again after she found that the only reason he hate Christmas is because he had a sad past and Cindy think that he's funny and not afraid of him which it upset him, but The Grinch decide to go to the celebration.
As the movie continues, The Grinch went crazy, got revenge, decide to stole Christmas and realized what he had done after realized that Christmas isn't about presents, but spending with your love ones.
At the ending, he return the gifts and got a kiss from Cindy who care about him. Then they become best friends as the movie ends.
Cindy Lou loves her parents and two older brothers, but she believes that everyone is missing the point about Christmas by being more concerned about the gifts and festivities.
After meeting The Grinch and knows that he had a dark past which she feels bad for him since he was bullied by The Mayor and the other Whos. She decides to bring The Grinch back to Whoville and make everybody include The Grinch to show them what Christmas really about.
During the celebration, her mother was lost at the light contest (delete scene) and soon The Grinch came late, having fun and almost almost won over, May Who gives him an electric shaver as a present, reminding him of his awful humiliation at school.
May Who then asks Martha to marry him, promising her a new car in return. This causes the Grinch to openly berate the Whos for thinking that Christmas is about gifts that they will just dispose of later, in the hopes of making them too ashamed to celebrate the holiday.
He then goes on to ruin the party by burning the Christmas tree with a makeshift flamethrower (although his actions prove fruitless as the Who's have a spare tree, which the Grinch sees them erect before he leaves).
After the gifts were stolen by The Grinch, the mayor and everybody blames Cindy for ruining Christmas by letting the Grinch come to Whoville which it hurts her feelings until her father stand up for her and finally realized that Christmas isn't about gifts, but spending time with your love ones and know that Cindy was right about Christmas and know the true nature of The Mayor.
While her family singing, Cindy goes to Mt. Crumpit and want to tell The Grinch about Christmas.
Then she was looking for him, but decide to go in the sled and saw him by saying hi to The Grinch which it surprise The Grinch that she came to see him and tell him that no one shouldn't be alone on Christmas. (It means that she always cared about him)
Then she smiles at The Grinch which it make The Grinch very happy that she does care about him until she was in danger of falling off the cliff with the sleigh, the Grinch finds enough strength to lift the sleigh, the gifts and Cindy Lou to safety.
After a long descent down Mount Crumpit, the Grinch returns to Whoville with Cindy and the gifts. He confesses to the burglary, apologizes for his actions towards the Whos and turns himself in to the police as they arrive, but the Whos reconcile with him, much to May Who's dismay.
Martha turns down May Who's proposal and decides that she would rather stay with the Grinch instead. The redeemed Grinch starts a new life with the Whos, commemorating the Christmas feast with them in his cave.
- She was the first Who (other than Martha May Whovier) who wasn't afraid and didn't hate the Grinch. She just knows that The Grinch is sweet and has a good side.
- Cindy Lou was afraid of The Grinch at first, because of his appearance. Then, later on, she realized that the Grinch had a tragic past (after he save her life from the stamping post machine) and trying to help him by becoming his friend which she did at the end.
- She was the first heroine (in Dr. Seuss movies) who gives the protagonist a kiss on the cheek at the end for bringing Christmas back, the second was Audrey for getting a tree.
- During the sled scene, not only Cindy Lou came back to see The Grinch again, but admits that she always cared about him and tells him that no one should be alone on Christmas which made The Grinch speechless and realized that he was wrong about her and knowing that he cares about her to after saving her life twice.
- Before the movie ends, Cindy Lou gently pulls on The Grinch's suit and thanks the Grinch for saving her and wishing him a Merry Christmas by giving him a friendly kiss on the cheek which it made the Grinch really happy since he haven't felt that kiss on the cheek for a while or something.
- Cindy Lou was The Grinch's first best friend along with his dog, Max in this movie.
- Cindy Lou was the only Who who understood The Grinch's feelings more than any other Who (other than Martha).
- Even though she's a child, she admitted why she cares about The Grinch when she met him: he saved her life, makes her laugh, thinking that he's more sweet rather than being a grouchy creature.