Routing Vnet B Resources through Vnet A Gateway for On-prem Network Communication

As mentioned by Anas you can do this and it is called transitive routing through the VNET where you have the VNG deployed. When you check the use remote vnet gateway in the peering then routes learned on that VNG will be propagated to the peered networks by default.

In case you have a filtering device like azure firewall or a third party firewall then you need to disable that option and configured UDRs manually pointing to the firewall or NVA IP address.

In the peering ensure this options is checked too:
Traffic forwarded from remote virtual network : Allow

Thanks.