The most obvious issue is the Internal Revenue Code prohibition on intervention in political campaigns.  A 501(c)(3) charity can lose its exempt status for “electioneering” if it participates in an election campaign.  Therefore the organization cannot endorse her, contribute to her campaign, or provide any other organizational support.  (See Ready Reference Page: “IRS Issues New Guidance on Electioneering”) She should not do anything political on company time while being paid by the organization.  She should do everything political after hours, or while taking vacation, or, better yet, while on uncompensated leave from the job. She should not use any company facilities for political purposes, including her office, her company-paid cell phone, the office copier, its mailing lists, etc.  None of the other paid staff should provide support during work hours and while they, the directors and other volunteers may personally endorse and support her, they should never suggest that the organization itself is involved or use organization resources to do so.

The less obvious issue is state or local election law that is likely to prohibit corporate contributions to election campaigns and could actually make some of the expenditure of corporate funds described above a criminal offense.

If the organization were exempt from federal income tax as an advocacy group under section 501(c)(4) of the Tax Code or a trade association under section 501(c)(6), an endorsement would not jeopardize exempt status since the prohibition applies only to 501(c)(3) charities.  But the expenditures could still violate election law if they are made for her campaign and not to an uncoordinated political action committee.