It depends, if her poo has always been this colour then i wouldnt think its anything to worry about. Do u breast feed or use formula? I know it can be quite normal for breastfed babies poo to be green. If not, have you switched formulas recently? Could be that if u have. Otherwise it could be an early sign of colic, a tummy bug or you may be over or under-feeding her. Oliver's poo was green once, doc said it was cus of his colic.
Check this site https://www.babycentre.co.uk/baby/dailycare/yourbabyspoo/
Tells u whats normal and whats not. But if you dont think its right call ur GP or HV. X