Assalamu alaykum wa rahmatullahi wa barakatuh Ustadh Ahsan Allahu ilayk Can a Woman wear her hair in a bun or a ponytail while praying? Or does she have to have her hair loose under her Khimar?

Ustadh AbdulAziz al-Haqqan

The salah is correct. There is nothing obliging her to loosen her hair.