I have come across many pups that eat stones, it is very worrying and something that needs stopping asap (my friends dog used to like the taste of concrete!!!!) It really is a hard habit to break, whether we broke it or she grew out of it i'll never know - but it did stop, I suspected that maybe their was something missing in her diet - but that is just my opinion and not based on fact!

The foods you mention are pretty cr*ap, and yes you pup should be on three of four meals a day, if she is only eating a small portion of the amount recommended for her size/age/weight you really need to speak to the vet, as there could be some underlying reason for this.

But if I were in your shoes I would try and get her onto a top quality food/mix at the earliest opportunity, pups should be fed specail puupy food in my opinion and I would use a mix of Nature diet puppy (wet) and one of the better complete dry - my choice would be Arden Grange - but their are many good quality foods available.
regards
DT