Is it obligatory to perform ghusl upon waking and finding something resembling semen, despite not recalling a wet dream and the absence of a distinctive odor of semen after it dries?

If what the woman saw does not match the descriptions of semen, then she is not required to perform ghusl, nor is she required to re-perform her prayers. The questioner is advised to turn away from whisperings (waswas) and not pay attention to them.