My mother lives with us in Kentucky. Her sister wants to pay part of the cost for her care. The sister lives in Florida. Can she get tax credit?

[Coleen3]

Unfortunately, no. She would have to claim her as a dependent.

Qualifying Relative

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

• You provided more than half of their financial support. More info
• They made less than $4,150 in gross income during 2018 unless they are a qualifying child.
• They live with you or they are related to you. (Your relative must live at your residence all year or be on the list of “relatives who do not live with you” in Publication 501.) 
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren't (or won't be) claimed as a dependent by someone else.
• They aren’t filing a joint return with their spouse.
• You are not being claimed as a dependent on someone else's return.