"Her father's name is Peter."
Translation:उसके पिता का नाम पीटर है।
'उसके पिता' is in the oblique case. This is when a noun is an object of a postposition (in this case का). The oblique form of उसका is उसके.
For me it only shower उसका as an option but isn't that wrong in this case? I'm confused..