Lily's father is English, the son of Greville Philip Austin Collins and June Collins (born Winifred Strange), a talent agent. Lily's maternal grandfather, Jack Tavelman, was born in Winnipeg, Manitoba, Canada, to Jewish immigrants from Russia. Lily's maternal grandmother, Billie Jane (Shoaff), was American-born, from a family from the Southern United States, and had English, and a smaller amount of German, ancestry. She was featured at We Day Seattle 2015 as Bystander Revolution's Ambassador and delivered a speech about the power of consistent, simple actions to affect change and shift the culture of bullying toward kindness. I just did a film actually in Dublin where I played British, so it was lovely to be back in my natural accent, cause I haven't had one since I was five. My natural accent when I was little was British and then, when I moved to the States, everyone made fun of me and I just adapted to an American one and now this is what comes out of my mouth. Now it's just a bit of a hot mess.
In her book Unfiltered: No Shame, No Regrets, Just Me she revealed that as a teenager she suffered from an eating disorder and wants to open up a conversation which affects women and men around the world. Lily is an outspoken anti-bullying advocate and became anti-bullying organization Bystander Revolution's first Ambassador in 2014. [on her eyebrows] It used to bother me - having bigger, fuller brows. I even plucked them once so I'd fit in, but I hated them and couldn't wait for them to grow back. Now I embrace them. I realized the quirky things that make you different are what make you beautiful. I've just turned 24 but I'll always be their little girl. My dad started as an actor. It's close to his heart. It excites him to see me taking on roles about growing up but, yeah, kissing scenes aren't easy for him. And in Stuck in Love (2012), I take my top off, so that was awkward.