H4 petition and stamping

Job change in 2017:


H1B visa petition approved after changing job (employer A to Employer B) and now valid till Oct – 2020

H1B stamp is valid till Oct 2019 since I went to India alone in 2016


H4 visa petition valid till Oct 2019 which was filed by old employer A

H4 visa stamp was valid till Sep 2016 and now planning to travel to India for a month. What does she need for visa stamping and can she avail visa waiver program?