Transfer H1B before stamping in home country

My fiance is currently working for a company on an H1B VISA and she has an offer from a new company. The new company is not experienced with H1B VISAs. Will my fiance need to get her H1B VISA stamped on her passport (at a consulate in her home country) before she can apply for a H1B transferto her new company? Or can she get it stamped after the petition by the new company is approved. It would be really helpful if you could clarify this

No need. They can apply for transfer in US itself and work for the same. You need visa stamping to re-enter US. If they already have H1B stamp from previous company and valid they can use that same to re-enter, if it is valid during re-entry. Read H1B Visa Transfer Process