Is it permissible for a woman to perform ghusl (ritual bath) with the intention of ihram in Medina, then perform wudu (ablution) and pray the two rak'ahs of ihram at the miqat, or is it obligatory for her to perform ghusl at the miqat? And is it permissible for her to comb her hair after ghusl, even with the possibility of some strands falling out?

The ritual bath (ghusl) for Ihram is a recommendable act, not an obligatory one. So, whoever omits it, their Ihram is valid, and there is no sin upon them. And whoever performs the ghusl has followed the Sunnah, and whoever limits themselves to ablution (wudu) has done well. The ghusl performed in Madinah is sufficient if it immediately precedes one's departure to Dhul-Hulayfah for Ihram, provided the interval between them is not long. However, if the interval is long, the ghusl will not be sufficient. There is no harm in combing one's hair after ghusl and before Ihram, even if some hair falls out, as it is recommendable to cleanse oneself and remove any hair that needs to be removed before Ihram.