We don’t pray to mary.
She prays for us.
She prays for us.
Official Catholic teaching is that Catholics do indeed pray TO saints (for intercession, of course).
As a non-Catholic (former Catholic), I've defended Catholics on this point as to the reasonableness of the position. (I assume saints are indeed living and can hear us).
Where I differ with my Catholic friends is with respect to the efficacy of asking Mary or another saint multiple times to "pray for us." When I ask a friend to pray for me, he hears it the first time. I don't have to call him 100 times within the hour and keep asking him again. :-)