Is it permissible for a Muslim male coworker to help a Muslimah sell girls scout cookies (for her daughter’s school) within the office?

All praise be to Allah and may His blessings and peace be on His last messenger, Muhammad,

As a general rule, it is permissible for a male or female to help his co-worker (male or female) to sell any product as long as there are no other factors rendering the act unlawful (such as temptation, prohibited products, breaking office rules, etc.). Allah says: “Allah says: “Help you one another in al‑Birr and at‑Taqwa (virtue, righteousness and piety); but do not help one another in sin and transgression. And fear Allah. Verily, Allah is Severe in punishment” [al-Maa’idah 5:2]

Selling cookies is a way of supporting various organizations. If the organization represents views that are entirely unacceptable in the Sharia (Islamic law), then it is not permissible to support such organization. I would, also, advise the sister to ensure that her daughter is not exposed to ideas or practices that could compromise her faith or religious commitment.

Allah knows best.