A friend close to the One Direction member speaking to The Sun described the leggy brunette as 'gobby but laidback'.
'Louis can't believe his luck,' they added, 'He is in awe of how fit she is. They've been out on a few secret dates so he's getting stuck in.
'She is a couple of years older than him but the lads in the band think she's the female version of Louis. She isn't afraid to bend the rules - just like Louis. It looks like she could be serious girlfriend material'.
Calder is about to go into her Sekunde Jahr at Manchester universität where she is studying politics and sociology - proving she is Mehr than just a pretty face.
One Direction are currently enjoying success in the charts with hit single What Makes Du Beautiful and are set to perform at the Radio 1 Teen Awards.
The five lads were recently treated to luxury apartments in London at the expense of their manager Simon Cowell, which include a shared gym and private cinema.
