Yup, the xyz university should agree to release her sevis record in which case she would be able to go to ABC university. If not as others said the visa and sevis is both tied to the XYZ university. I know someone that has gone through the similar situation: applied for a school in KS; had relatives in NE; asked school in KS to release her sevis they did and she started going to the school in NE from the get go. Hope this helps and good luck. :)