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.