Lily Aldrin is one of the most divisive characters in How I Met Your Mother. After all, there are countless instances when she was the most immature person in her friend group. From lying to Marshall to manipulating Ted's relationships, Lily was growing worse and worse with every season and very rarely had to own up to her mistakes.
Her behavior often resembled that of a child. Luckily, she was surrounded by people who were willing to clean up her messes and accepted her for who she was. Because in the end, she wasn't just immature - she was also friendly, funny, and adventurous.
The 'You're Dead To Me' Look
While Lily had every right to give her neglectful father the 'you're dead to me' look, she also used it on other people. At her wedding, she gave her own bridesmaid Whitney the glaring look just because she said that she doesn't like strapless wedding dresses. Among her other 'victims' were her neighbor and a man who served her regular coffee when she explicitly asked for decaf.
It's perfectly fine that Lily stood up for herself and didn't allow others to walk all over her, but that being said, she really should have worked on her communication skills and healthy ways of setting boundaries. Staring people down instead is extremely immature.
Her Attitude Towards Marshall
Lily was a loyal and loving partner, but she was also unnecessarily possessive and territorial. Marshall never had eyes for another woman and would never cheat on her, yet Lily was willing to throw fists to show that he was only hers.
She had a double standard: while Marshall could barely talk to other women, Lily had no qualms with flirting with other men and taking her ring off to see how much attention she'd get. Additionally, she proclaimed herself as the settler, even though fans generally agree that it's Marshall who deserved a better partner.
When She Wrecked Marshall's Car
Lily and Robin once spilled something all over Marshall's beloved Fiero, but instead of owning up to their mistake, they decided to damage the car even more and say that somebody broke into it. Lily didn't really care about Marshall's feelings about the car, she just wanted him to not be angry at her.
She Couldn't Keep A Secret
One of Lily's worst traits is that she cannot keep a secret, no matter how big or small it may be. While her complete inability to keep things to herself comes off as immature with big secrets, it's oddly endearing with smaller secrets. On the other hand, Lily has no problems keeping her own secrets at bay.
Getting Herself In Unnecessary Debt
One of the biggest secrets that Lily managed to keep just fine was the fact that she was addicted to shopping and got herself into completely unnecessary debt. As soon as she told Marshall, he started cleaning up her mess. But as childish as she was, she refused to sell her things to get out of financial troubles.
In the end, it was Marshall who had to carry this burden, and even then, Lily complained about it. He worked at a well-paid corporate job to make ends meet, while Lily complained that he was no longer the man that she had married.
She Proved That She Can't Work With Adults
One of Lily's worst story arcs was the time when she worked in Ted's company and served the so-called Aldrin Justice to Druthers. While this particular learning approach might work in kindergarten, Lily failed to understand that it's highly unprofessional and juvenile to exercise it in a different kind of work environment.
On the bright side, Lily realized that she preferred working with children after this unfortunate event and went back to working at the kindergarten. It turned out to be one of the best career decisions she has ever made on the show.
When She Meddled With Other People's Relationships
Lily often took matters into her own hands, which is highly problematic as well as immature. After Ted found out that she broke him up with Karen, Lily also confessed to having a hand in several other breakups.
Initially, she handled the situation like a child, refusing to apologize. Eventually, she came around and even helped Karen and Ted get back together.
As A Parent, She Was Sometimes Irresponsible
There is no lack of questionable parenting choices in How I Met Your Mother, and Lily is no exception. Together with Marshall, she organized a game show to decide who would be Marvin's godparent, even though Robin didn't even like kids and Barney wasn't up for such a responsibility.
It also makes little sense that she and Marshall had enough time on her hands to still frequent MacLaren's Pub, but then again, the show would have been awfully boring if the couple was out of the picture after Marvin's birth.
She Refused To Hear Marshall's Side When They Fought
One of the biggest arguments on How I Met Your Mother happened in the final season when Lily and Marshall fought about their future. Lily had a chance to become an art consultant in Rome, while Marshall was offered the position of judge. It was a no-win situation: both were equally stubborn about their point of view, but Lily in particular didn't want to hear Marshall out at all. She got her way by being selfish and immature, not by having a constructive conversation.
It's important to consider that everybody else in the group got to live their dream lives, so it's only fair that Lily also got what she had always wanted rather than sacrificing her personal freedom. If she were to give up the opportunity in Rome, she'd undoubtedly grow incredibly resentful of Marshall.
When She Abandoned Marshall
Seeing Marshall devastated on the stairs after Lily left him was one of the saddest moments in the history of the entire show. Lily handled the crisis extremely immaturely. This power couple surely could have handled a few months of long-distance, or better yet, Lily could have found ways to pursue art in New York City.
It's hard to judge Lily for having a moment of weakness, though. As she said herself, she's always done everything by the book and never made a huge mistake in her life. It's only human that she wanted to see what it's like to live on your own and pursue her passion. Otherwise, she might be sitting on that porch as an 80-year-old woman, ruminating all the 'what-ifs'.