Congratulations!
There are so many free patterns & tutorials online. I find googling in images much easier to find what I am looking for.
I have won a copy of Sewing for boys on a blog. But is hasnt arrived yet. 
It looks really good and suitable for girls also. There was a "http://www.patternsbyfiggys.com/2011/09/the-blog-tour-begins/ blog tour" where you can see some photos and projects made from the book.
Oliver and s do great patterns but they are quite expensive although there are a couple of free patterns on their blog. I have made the sailorboat top which I bought from backstitch.co.uk. and it came out really, really well for a novice.
Your mum could also try Japanese pattern books, Although the instructions are in japanese, they are meant to be very easy to follow if you have some dressmaking experience. You have diagrams/pictures to follow just like your IKEA furniture, an explanation here... and pattern drafting tips here
Serious 
at anyone who can actually make wearable clothes from any pattern!
I bought this book from the bookpeople, but it is nearly all girls stuff (I have 2 ds) and half the instructions were missing, like it just said "finish the placket" without explaining how! The projects are very easy but probaly not challanging enough for someone like your mum (simple tunics, trpousers & pillowcase dresses)
for cheap fabric try fabricland, but for really lovely fabrics try fabricrehab, seamstar, saints and pinners, sew me happy, backstitch and raystitch.