Islam does not prohibit women from serving or talking to non-mahrams while observing modesty and adhering to the teachings of Islam regarding dealing with people from the opposite sex.

The prominent Muslim scholar and Da`iyah Zeinab Mostafa stated: Islam does not forbid all mixing with the opposite sex, especially when there is a need for it. If a family is visiting another and they all sit together, talking modestly, observing hijab, refraining from speaking too openly in a way that attracts a person from the opposite sex, then that is OK.

It was related that the Prophet (peace and blessings be upon him) asked one of his Companions to host someone who did not have anything to eat.  The Companion, as it was narrated, asked his wife to join them at the table, turn off the lights, and pretend that she was eating, because they did not have enough food for all of them. This hadith is enough as an answer to your question. Had it been forbidden for a wife to sit with a non-mahram in the presence of a mahram, the Companion would not have asked his wife to do that.
Also, the Prophet’s wife Zainab bint Jahsh (may Allah be pleased with her) served the people in her wedding. She would bring the food to the men who came to congratulate the Prophet and her. Had it been forbidden for woman to mix in that way, she would not have done it.
It is allowed for a woman to interact with and welcome her guests, whether men or women, as long as there is no khulwah (seclusion of a woman with a non-mahram) and the Islamic codes of conduct in public are observed. So, there is no need to create unnecessary mischiefs.