Help about good materials and studying strategies

Hi everyone ,

I am wondering whether someone can help me . My fiance took the test and did not reach the desirable result. She did the OG 13 twice and the Gmat Prep question Pack twice as well. She took both practice test and all the Manhattan tests. Does anybody can recommend some other materials?

- Question Banks Gmat club , Knewton, Veritas?

besides that , are there more good materials??

Studying strategy?? any advices?? She was scoring 620 / 630 in the Practice tests. Her official score was way too far from that , any tips or recommendations? She is targeting at 650.

Thanks in advance for any help!!!