From what I can tell, many women prefer pressure to vibration for g-spot. If she doesn't like glass, check out ceramics (I don't have any experience with the line LH is currently carrying so can't recommend anything from that in particular) and silicone. Did she look at the Ella? It's a lovely thing.
If she's convinced she wants vibrations for this, then maybe look at the Rock or Groovy Chick (which one is best for her depends on her particular shape or start experimenting with eggs.