MDF will support granite just as well as a plywood base. You will be fine with whatever top you choose. Good luck.

I know in the kitchen, it's not recommended to put granite over MDF.

Where did you hear that malarky? If you couldn't put granite on MDF, then 50-75% of the granite tops in kitchens and baths would be falling down. Meaning that a large majority of cabinets nowadays are made of MDF.

I'd make sure that vanity is tall enough that she won't have to lean too far over. I love my higher height vanity that I built.

Thank you for the replies. Well, turns out the vanity isn't MDF anyway. According to the packaging, it's all wood construction. Could have sworn it was MDF (I ordered it through Hayneedle) but then again by the time I came across this vanity, which seemed to be the perfect marriage for what mom and I both wanted / needed, I was on vanity overload so might have gotten things mixed up. Oh and it also had left-side drawers. We wanted drawers but they needed to be on the left side due to the plumbing.

For now, I've decided to go with a cultured marble top / sink.

Cook's Kitchen thanks. I knew what MDF was but never thought that it would be described on the side of the packaging as all wood construction. And I've never considered plywood all wood construction. Funny thing is I have a tendency to opt for MDF over plywood even though I think plywood is supposed to be an upgrade over MDF. I've just seen one too many cheaply made plywood cabinets.

I ended up getting a cultured marbled sink from Lowe's. I love the white on white look. I'm really not a fan of granite but I wanted to be able to explore all my options in case I came across something I just couldn't live without.

Now, I'm waiting on the new faucet to come in (Lowe's) and the flooring (Tarkett vinyl through Carpets to Go), then I should have everything on hand so I can finish up this project.

Since this bathroom wasn't a planned remodel and the first time I've done anything like this, I've learned a lot. When I do the master bath, which before this I had planned to do next year, it should be a different experience since 1) that is a planned remodel and I already know / have ideas of what will happen in there and 2) will take the knowledge from redoing the bathroom that Mom uses and apply it there.

No one has ever made cabinets without either plywood or MDF unless they're metal. Solid wood is not dimensionally stable enough. You have to go back to 19th-c and before style-rail-panel construction to avoid failure. Which has never been done with a fitted kitchen.

Thanks Milly, that puts the information about wood, plywood and mdf in perspective.