Is it okay to report my aunt who is not handicapped for parking in handicapped spaces
Why do you want to report your aunt for using handicapping parking?
She uses it to park closer to the entrance even though she is not handicapped.
First off it is wrong to break any rules. What makes it worse is breaking a rule by taking away a service for handicapped people who need the parking space. So it is acceptable to report your aunt.
Her sister is really handicapped, but my aunt uses the spaces even when she's not with her sister.
Your aunt isn't allow to use the handicapped space if she's not with her sister, so you should still report her if that's what she's doing. It'll be good for her to get reprimanded, so she can learn how important it is to leave those spaces open for people who need them.