Every IPv4 address has its own IPv6 /48 automatically assigned to it. Forget getting more adoption, apparently it wasn't even enough to stop people from suggesting that v6 should've done something it already did!
Generally, if it's not being routed right now on the public internet, and just used inside networks for migration purposes, it's not as useful for the "my Minecraft server has this IP" use case.
This means she'll have to either send an IPv6 header or an IPv4 header with a false or blank IPv4 from address. If she sends an IPv6 packet, Bob's IPv4 network stack won't be able to understand it and drop the packet. If she sends an IPv4 packet with a blank or false IPv4 from address, Bob will receive the packet, but won't be able to send a response.