Lunch w a female. Some times nothing wrong with it and sometimes? So it depends on his intention. Talk. About this issue and try to iron u differences.
Yes. It is possible for men & women to be just friends. Lunch with a co-worker usually is just lunch. It's not a date. If you feel you can't trust your boyfriend with this female, ask yourself why. Is it because you can't trust yourself? You can't trust your boyfriend? Has he done something to make you think you can't trust him? You trust this co-worker? Whatever the reason, talk about it.