My dog has a back problem and walks funny. How can I help her?

First I would recommend to have Cloud examined by her veterinarian. Cloud is old enough that she may start to exhibit the beginning signs of hip dysplasia or other growth abnormality. Large and giant breed dogs are prone to the issues and the issues are best addressed while the pet is very young to avoid permanent changes to the body. The veterinarian will need radiographs to look at the joints and determine what to do next.
At home you can give her supplements. Start giving an omega 3 fatty acid (Nutramax makes a nice product) can help with natural inflammation control. Make sure to get one meant for pets.
Go ahead and start her on a joint supplement. Dasuquin is a good product for the joints. It will help to keep the inflammation in the joints lower and this will decrease pain.
If you are interested in a diet change, Royal Canin makes a diet called Mobility Support which has green lipped muscle as an ingredient and pets tend to do very well in it. You cannot use this though until Cloud is adult sized as it is not formulated to support growth of puppies.
I hope this is helpful. Please feel free to post any additional questions.