she should definitely check up on her application
she should call the INS Customer Service Center, 1-800-375-5283.
She could also contact her local district office. bring a letter in writing requesting information to be place in her file.
If your friend moved after filing her application, she should send a change of address notification. She should bring this with her if she goes to the district office.
Considering the application was filed 3 years ago WITHOUT receiving a Notice of Receipt, she should verify that her check/moneyorder was actually cashed. If the money order/check was NOT cashed, the INS probably never received the application.
If it was cashed, she can use it as evidence of filing, when she contacts the INS: send copies of her evidence of cashing, not original documentation.
However, If she changed her address soon after filing, she may find that the INS has already denied the application for abandonment. she can then request INS reopen the application based on her not receiving notification from the INS (might work & costs nothing), she could then file Motion to Reopen (with fee) or file a new application (with fee).