I love my Grandma, but she is a bit much to take care of. Any advice?

Your family looks to you as the caregiver for the unwell.

Where is your Mother and Father ? You need to get on with your Life . 65 is very young . Does she need a psychiatrist and medication ? Do you have goals for your life Like college ? Try to find a social worker or someone you can confide in for adult advice . Your Grand Mother is not your problem . Maybe a Hospital clinic is where you can find a social worker . I went to a Hospital once and got a therapist and a psychiatrist . Eventually you find support groups . There are many different groups - womans groups , Al Anon - even try Yoga or holistic healing Modalities like Reiki . There are Places to go for work study Like Omega institute in upper state NY in Rhinebeck that is a summer retreat - they have Blue spirit in Costa Rica , Ojai foundation in California , Mount Madonna in California . There is a Cute Place Mountain Light sanctuary near Asheville , NC . Hawaii has farms you can work on . This is your time to make your dreams come true . I would start saving some cash and filling out some applications and leave this mess behind. Your sister will be fine . Really 19 is when your Life begins . Walk away when you get accepted for a Job and dont Look back .

Get a job and stop caregiving. You're way too young to be throwing your life away for no reason.

According to your profile your grandma is only 65 years old and has no major health issues, so why do you feel that you're caring for her?
Someone at your grandma's young age with OCD, depression, hearing loss and mobility issues doesn't really need someone to care for them. She should be able to care for herself just fine.
You mention in your post that she's mentally incompetent, but how do you know? Has she been diagnosed with any mental decline?
You don't give us much to go on, like where your parents are, and why you're having to supposedly take care of grandma and your sister, but bottom line, your grandma is NOT your responsibility, nor does it seem like she really requires any care, so get on with living your life and take care of you. And let the actual adults in your family take on any care that your young grandma may need, though again, nothing you've listed says that she requires any care at all, so let her live her life as well and take care of herself.

What is the living arrangement? Whose house/apartment are you living in?
Or does your Gramma live somewhere else & you go there to care for her?
Do all 3 of you live together?
Who is the legal guardian for your sibling and where does this person/s live?
Why are you taking care of this sibling?

The answers matter in what helpful advice we give you. thx

Why are you taking care of grandma and why has it been so long? Where are the 'grownups' in this situation?

You need to finish school and take care of YOU before you care for others. I'm gonna give you a pass, sort of, on the caring for your little sis. (My mom routinely stepped out of 'momming' and left caring for my 3 younger sibs to the wind. I stepped in many times and did what had to be done, but there is a measure of anger towards that kind of situation...50+ years later!)

So for 4 years you have been caring for Gma and little sis and I assume you have not been paid, right? You're doing this because someone has guilted you into feeling that this is what family does.

First off, come back with deeper info. We need to know more about the situation before anyone can really step in and help you.

Are there parents around? Do you live with gma? What's her health situation, besides the paranoia? How old is she? Things like that--we can't help you until we know more.

Good Luck!