The 'Starry Eyed' hitmaker has toured the US supporting the singer and says his live show has made her ''up her game'' and improve her own stage set to be more suitable for a bigger audience.
She said: ''Bruno's show is phenomenal. It's the most incredible live show I've seen - that and Bjork, and it made me want to up my game.
''I read an article the other day that said I'd become Americanised, that I'd come from this shy English rose girl playing a guitar to being this big pop star... But you do adapt a bit to those bigger crowds and playing arenas. You can't just go out there and just say, 'Hiii'. You really do have to go out there and command.''
Ellie penned her 2012 album 'Halcyon' after splitting with boyfriend Greg James and though she admits her feelings now are very different, at the time she thought she'd never ''win in love'' again.
She added in an interview with Q magazine: ''I'd drawn to sadness, to sad songs. But there was just something deeper this time.. The saddest line I wrote on the album was, 'I know I'll always ache with an empty heart'. That summed up how I was feeling. I don't necessarily feel like that now. But I felt like I was never going to win in relationships or love.''
Take a look back at October's inaugural event.
The film is expected to continue without Mendes' involvement.