Bebe Rexha has a sibling-like relationship with Louis Tomlinson.

The 28-year-old singer-songwriter and the former One Direction star recently collaborated on the single 'Back to You', and Bebe has admitted the duo built a rapport instantly.

She said: ''The second I met him, he was kind to me and my team.

''He's just cool. I don't feel nervous around him - he's like a friend now, and it's cool to work with friends.''

As well as collaborating with Louis, Bebe has also worked with country act Florida Georgia Line on the track 'Meant To Be'.

And Bebe says that experience has transformed her perception of country music.

She told Billboard: ''I think it changed my mind about music in general.

''I'm learning that music business is based off of just great songs.''

Bebe's confession comes shortly after she admitted she hates working inside creative ''boundaries''.

The American star revealed she doesn't enjoy being pigeonholed as a musician, while she also admitted she didn't relish writing for other artists who were asking her to produce a very specific, radio-friendly sound.

Bebe shared: ''Back in the day everything was so specific to the 'type' of artist you were.

''This is what you look like, this is what you sound like, it was like boom-boom-boom. Being a writer at the time, it was actually hurtful because people would be like, 'Wow you're stuff is too everywhere, who are you?'''

Bebe has previously co-written hit tracks like the Eminem and Rihanna single 'The Monster'.

But she has experienced some frustrations when she's been asked to pen songs for other stars.

Bebe explained: ''When I was just doing songwriting they would send me sheets, and they would say things like, 'This artist is looking for this, there's a new girl group and they're looking for something that sounds like Rihanna meets Christina Aguilera and Coldplay, or whatever, and we want this type of vibe.' But I don't like boundaries.''