H4 Travel while H1 transfer in Process

Hi, My new employer applied for H1b transfer on Nov 26th. I have received the I-797C for my wife and son. That’s the receipt notice. My current h1 is valid till Feb 2015. Following is the concern 1. Can my wife travel before I receive the Approval notice. 2. If she can travel, will her H4 petition be abandoned. 3. After approval, while she comes back a new visa stamp required? Thanks.