Your GF could possibly be claimed as a qualified relative dependent on your tax return if she meets the criteria--including that she had to live with you for the entire tax year, and had less than the limit for her own income--which would not include Social Security. If you claim her, it will be for the $500 credit for other dependents.
https://ttlc.intuit.com/questions/4499708-what-is-the-500-credit-for-other-dependents-family-tax-cre...
If she met the criteria for a past year, you could amend your return(s) for those years. For 2016 or 2017, you would also get a personal exemption for a dependent that you claimed. As of 2018 returns, there are no personal exemptions.
WHO CAN I CLAIM AS A DEPENDENT?
You can claim a child, relative, friend, fiance (etc.) as a dependent on your 2019 taxes as long as they meet the following requirements:
Qualifying child
• They are related to you.
• They cannot be claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They are not filing a joint return with their spouse.
• They are under the age of 19 (or 24 for full-time students).
- No age limit for permanently and totally disabled children
• They live with you for more than half the year (exceptions apply).
Qualifying relative
• They don't have to be related to you (despite the name).
• They cannot be claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They are not filing a joint return with their spouse.
• They lived with you the entire year.
• They made less than $4,150 in 2018 (for 2019 it is $4200)
• You provided more than half of their financial support. More info
When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
