Hello Vivien, " I have date a girl who is chill" 'chill ' means " cool", he dated a cool girl. " I have dated a girl who is laid back, but still hot." A person who is laid-back is very relaxed and does not get anxious or angry very often. "hot" here means attractive ,sexy and exciting. He dated a girl who is cool and relaxed , yet is temperament ,sexy and exciting at the same time.

Hi Vivien, 'chill' can also mean 'chilly' or cold meaning not very responsive. 'Laid back' can also mean calm and not worried about anything, yet very exciting and attractive[ hot]