I had trouble with my daughters algebra (Yuk!). Went on this site and was able to help her with it:
http://www.bbc.co.uk/schools/
There are other sites too. Put the type of maths you are doing in google and it will find some sites that maybe helpful.
There are many books you can buy from the likes of W H Smith on all subjects in all key stages. A Tutor is not such a bad thing. My daughter had one for science for a short period, gave her lots of confidence. No one needs to know about it.
You need to let your daughter know that she is not useless and that a lot of children and adults struggle with maths. You need to point out what she is good at and praise her well. Take her to the book shop with you to choose books on maths, let her look and decide or at least let her THINK that she has decided which one is the best. Stick at it. Good luck.