Is the Tawaf Al-Ifadah valid if a woman performs ghusl and circumambulates while she is not certain of her purity after seeing a yellowish discharge, and then a viscous, brownish discharge appears, especially given that she suffers from obsessive-compulsive disorder?

Your wife's circumambulation (tawaf) is valid, and she is not required to repeat it. Her Hajj is also valid, God willing. What is obligatory upon her is to perform ghusl (ritual bath) whenever she sees purity through one of its two signs: dryness (jufūf) or the white discharge (al-qaṣṣah al-bayḍāʾ). The criterion for dryness is that if a piece of cotton is inserted into the area, it emerges clean, with no trace of blood, yellowish discharge, or brownish discharge. The presence of normal moisture does not harm. This is the purity your wife saw, so her ghusl and tawaf were valid. As for the brownish discharge she saw after that, it is considered menstruation according to the Hanbalis, and her acts of worship that occurred during the intermittent period of purity are valid.