Is a girl sinful if she repairs devices and creates new accounts for their owners, if these owners then use these devices for disobedience, and is she absolved of responsibility if she warns them beforehand?

Repairing devices and setting up accounts to download programs onto them is permissible, unless it is known that someone will use them for unlawful purposes. In that case, assisting them is not permissible. A mere possibility that the device might be used for unlawful purposes does not prohibit assistance.