If she qualifies as a dependent you can claim her :

Who can I claim as my dependent?

You can claim a child, relative, friend, or fiancé (etc.) as a dependent on your 2018 taxes as long as they meet the following requirements:

Qualifying child

• They are related to you.
• They aren't claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t 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).
• They didn't provide more than half of their own support for the year.

Qualifying relative

• They don't have to be related to you (despite the name).
• They aren't claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They lived with you the entire year.
• They made less than $4,150 in 2018 ($4,250 in 2019).
• You provided more than half of their financial support.

When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them.

Related Information:

• Does a dependent have to live with me?
• What does "financially support another person" mean?
• Can I claim myself or my spouse as a dependent?
• Can I claim my parent as a dependent?
• Can I claim a newborn baby?

You may be able to claim her as a dependent under the Qualifying Relative rules if she meets all the requirements.

To be a Qualifying Relative -

1. The person cannot be your qualifying child or the qualifying child of any other taxpayer. A child is not the qualifying child of any other taxpayer if the child's parent (or any other person for whom the child is defined as a qualifying child) is not required to file an income tax return or files an income tax return only to get a refund on income tax withheld.
2. The person either (a) must be related to you or (b) must live with you all year as a member of your household.
3. The person's gross income for the year must be less than $4,200 (social security does not count) in 2019
4. You must provide more than half of the person's total support for the year.
5. The person must be a U.S. citizen or a U.S., Canada, or Mexico resident for some part of the year.
6. The person must not file a joint return with their spouse.