My Wife Is on h1b. Can She Take a 1-Week Summer Job in Her Field at Another Employer?

It is difficult to answer this question without more details, but generally an H1B visa holder can have more than one job as long as there is an approved H1B for each job. So, an individual can have multiple H1Bs. In addition, if an H1B visa holder decides to change jobs, then it would be necessary to file an H1B transfer application for the new job.