"It is not easy for someone to inject ones own butt."
Right, besides...the abcess was in her left buttock. She's right handed.
You can do both sides but it involves a lot of twisting your torso. And you can only get to the top outer quadrant, which I think Anna would have called her hip. She wouldn't have had the pain in her "buttocks" as claimed. I do not think she self-injected. I don't even think she self-poured a glass of juice.