The Virginia state legislature was comprised of the legislators that remained loyal to the federal republic.<quoted text>'as well as' meaning both. The Virginia state legislature never gave their consent. And if you deem the legislature now resided in the counties that formed West Virginia, the mere fact that they formed another state suggests there was already an existing state and in turn and existing state legislature for the state of Virginia. So what they created(West Virginia) was unconstitutional.
The "other state" did not exist until it was authorized by the federal republic. The legislators that remained loyal to the federal republic became the legislature of the state of Virginia. The legislators that rebelled against the federal republic and became a functioning element of another country did not comprise the legislature of the state of Virginia as recognized by the federal republic the rebelled against and declared their standing as not being part of that federal republic.
Thus, those legislators that did not rebel had the authority to represent the state of Virginia in the federal republic, and had the authority to petition to split the state of Virginia into two separate states.