Is this a sign of pregnancy or urinary/yeast infection?

so my sister let her bf finished in her two times. the beginning of the month And close to when shes due to get her period. she is taking necon birth control. now she is gettin white discharge, which sometimes smells sometimes doesnt, and is feeling a sight burn in her private part.... i feel like shes not going to know until she gets her period next week. but just some opinions for her sake. personally i think she was stupid for doing that and im younger than her! but she needs help without going to a doctor yet.