Student Visa-Permanent resident application conflict

[stuvis]

My mom has applied fro my sister permanent residency. The application has not been approved yet. She just got an admission from her dream univeristy to pursue her masters degree. Given that the permanenet resident application has not yet been approved, should she mention anything about that at the embassy when she goes for interview for her student visa? If so, how would that affect her studet visa processing.
Ive been told that since the application hasnt been approved, she has no obligation to mentione that.
Please advise.
Thank you.

[kabkaba]

In the DS 160 application that she will submit, there is a question about whether any immigrant petition has ever been filed for her. She will have to answer 'yes' to that question.