When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
Federal and state returns must be in separate envelopes and they are mailed to different addresses. Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.
you may also want to include form 14039 identity theft affidavit
As for claiming your GF----if she lived with you the WHOLE tax year and had less than $4300 of income (not counting Social Security) you may be able to claim your GF as a "qualifying relative." You would get the $500 credit for other dependents for claiming your GF.
Your own child may be claimed as a qualifying child.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
https://ttlc.intuit.com/questions/3113432-who-can-i-claim-as-my-dependent