Dealing with a Possessive Dog
First off, I would not give her rawhide bones anymore. Guarding bones falls under the category of "resource guarding". Dogs can view all sorts of things as resources like: you, comfy sleeping areas, food, toys, personal space, etc. If that particular bone was very high-value to her and she guarded it, but normally does not guard items, I wouldn't worry too much but would take steps to work on her guarding behavior. If she guards numerous things you'll need to work hard, immediately, to fix it. Having a small child in the house makes it a lot more dangerous and they should NEVER be left together unattended. Working with a trainer or behaviorist on this problem is a good idea. They will help you recognize the signs that she is uncomfortable so you can get her (or your son) out of the situation before it escalates. There is a great book by Jean Donaldson called "Mine: A Practical Guide to Resource Guarding" that tells you step-by-step how to work on it. Some people find it a bit overwhelming, but the author makes sure that you never progress faster than the dog can handle. Resource guarding is a "fixable" problem, but it will take effort.