Man,do you really trust those Instagram contests?
Sounds like a marketing gimmick to me.
Contests in Instagram are real for sure,I did participated but the rewards are not much expensive like this one but check the page which got 372K followers so they might got real sponser for this content.
I don't think that they are all reliable.
Especially those who give expensive gift such as a smartphone for example. I have won one contest in the past but the reward wasn't expensive.
Anyways I gave my like, good luck to your sister!