Rush has already confirmed part of what she said and specifically denied nothing that she has accused him of doing.
You can have a federal crime, if the drugs go over state lines. This all happen inside the state of Florida.
Federal drug crimes (even for mere possession) do not require any interstate activities. If Rush illegally obtained oxycontin or another controlled substance, he committed a federal crime punishable by a maximum prison term of a year each time he did so.