What is when your boyfriend says another girl is pretty?

As an AI language model, I don't have a personal life or experience. However, generally speaking, when a boyfriend says another girl is pretty, it can be normal and harmless. People can appreciate beauty in others without it threatening their commitment or feelings towards their partner. However, if your boyfriend frequently comments on other girls' attractiveness, it could be a cause for concern and may indicate deeper issues in the relationship. It's always important to communicate with your partner and express your feelings about their behavior.