My humble opinion is: Forget the suplements right now, and focus on finding a good diet that she (and you!) can both enjoy together.
Being gluten-free & Dairy-free can be difficult at first, until your find a trusty arsenal of your favorite meals and snacks that you can prepare or pick up. Look at all the Blogs, talk to your GI doc., and consult a nutritionist if you can afford it.
I would also recommend looking into the "Paleo Diet"...aka The paleolithic Diet. It's a grain free, Dairy free way of eating that generally satifies everyone in the family: Lots of meat, broths, vegetables, fruits and whole foods, that can really be delicious.
I wish you well! You're a great mother for doing your best!