I’m of the same opinion that *if* Anna trapped Elsa in the urn it was either accident or she was told it would save her life – something along those lines. I don’t think Anna would ever turn on Elsa. The Snow Queen seems a bit of a sneaky biscuit so I wouldn’t trust her with the truth.
Also why is Elsa not asking where Kristoff is?
My guess, since she seems to have lost her memories of quite a time, I think she’s still in the mindset of looking for Anna after she went to the EF. I’m assuming the last memories Elsa has were of her and Kristof in Arendelle waiting for Anna to come back, so she might think he’s safe (with Sven). Or, she’s just extra worried for Anna because she’s family and the person who helps her control her magic.
If one is to engage with the primordial forces of darkness, one must expect a little social awkwardness