To mail a letter to Parrin while she is in the MTC you can send your letter to:
Sister Parrin Habibpour
Oct 7 Bra-Cam
2009 N 900 E Unit 136
Provo, UT 84602
And if you don't want to go through the postal service just go to dearelder.com and type up a letter for her and they will print it and send it to her. You will need her unit number, which is 136.
I will update this post as her address changes.