Your mother is not a good mother to you and will never be barring some sort of epiphany from a higher power.
Most parents don’t cut their kids off at 18 but slowly push them into more independence until at around 23-25 they offer mostly emotional and babysitting support and financial help in emergencies only. At 26 you should be able to get along without a lot of help from your parents. But your mom has never treated you as her child and you can’t expect her to now. I understand that a lot of this gets harder to take as you become an older adult as you see what type of parents other people have. I come from a family where there were two favorite children and two children who got very little to no emotional or other support. She actively and openly disliked two of us.
Drop your mom, you’ll feel better. Interact with her only in regards to your sister. Build a group of friends who will support you and whom you support. Make getting a group of friends a job until you settle into some relationships: write on your calender reminders to call people, schedule lunches and get togethers. Even if she was a great mom and you could count on her she could die and leave you with nobody. I have no family nearby and even with very few friends here when I first moved I reached out to neighbors for help. People love if you ask for help and they can feel like they can ask you for help in return. The best friends I have are from weekly or biweekly activities because you get closer to people you have to interact with.
Good luck. Don’t call your mom for anything.

