Man or boy feel uncomfortable or insecure when their girlfriend flirts with another man or guy.
Flirting is not wrong or bad. Jealousy is like salt in food. A little can enhance the savor but too much can spoil the pleasure.
If your male partner feels something like this then talk to him, love him, and don't do it every time. It can destroy your relationship.
If your girlfriend does this every time, then talk to her share your feeling with her, if she not stoping it then she is not respecting you and not carrying about you.