Is the Umrah of one who exited her Ihram and trimmed the ends of her hair herself valid? And what is incumbent upon her if that is not valid?

If a woman performs Umrah in the prescribed legal manner, her Umrah is valid. It is not a condition for tahallul (release from the state of ihram) that her hair be cut by a mahram or a husband; rather, it is permissible for her to do it herself or for another woman to do it. If her journey for Umrah is a safar qasr (a journey permitting shortened prayers), then it is obligatory for her to be accompanied by a mahram, a husband, or a trustworthy and righteous group of women.