Translation:Her cat dances better than your dog.
Question: would the following be more "pure" i.e. without the use of English loanwords ("better" = "बेहतर")?
"उसकी बिल्ली तुम्हारे कुत्ते से अच्छा नाचती है।"
"बेहतर" is not an English loanword. It is Persian, and as such it can be considered a natural part of the lexicon that made up the Hindustani language from its inception as a modern language born of Indic grammar and lots of Persio-Arabic vocab.
To answer more directly though, I personally feel that your construction is more natural or idiomatic (and I've expressed this on another example)... though evidently that is a matter of perspective since the creators of the course didn't think so. My point would be that your construction is not more correct per se but rather more common. Interested to hear what others think.
Thanks RanzoG because I had NO idea! Totally was bugged because I thought it was Hinglish too.