Yes, if you were
printing only the forms required for the state that needs to be mailed, then
you should send them all.
The second state return is most likely being included if you claimed a credit for taxes paid to another state as a
part of that state return. When this
is the case, the state taxing authority wants to see a copy of the other
state’s tax return.
If that is not the reason that it printed both returns, then
consider it is better to send too much information than not enough and possibly
delay the processing. If the second state
return is not needed, it will just be discarded.