I mean it's not out of the realm of possibility. She could finish 6th but I think her PCS are too high for that to happen, even with a less than ideal skate.
You also don't know that she will/did "shake off covid-19 like it's just a head cold." And regardless, she would have to miss training time and hasn't been in form this year. I don't think you can say Liza had covid without also acknowledging Alena did too. And we don't know how that will affect either of them. At the minimum, it's affecting training time.
I mean we don't know how various skaters look like now, especially Anna, Liza, and Alena. However, based solely on the Russian Cup/Rostelecom, I would say Alena looked the least prepared and the one who looked like she was skating at her potential the least. Kamila, Anna, Sasha, Liza, and Daria have all looked stronger and have all had impressive moments where it looked like they were back in form or exceeded expectations.
Do I think Alena will finish 6th? No. (She'll get PCS from the judges and her spins/skating skills are absolutely lovely. Plus it's been a couple weeks since we've seen her. And she is the reigning GPF/European champion.) Do I think it absolutely can't happen? That there's no chance? Also no. (She doesn't have the PCS cushion she's had in the past. Also she doesn't necessarily have a 3A so won't have a short program advantage.) Even if Alena has her 3A, Anna isn't far behind her short program score (even without one.) In addition, Kamila, Sasha, and Liza have 3As they have attempted (and in some cases, landed in competition.) It's not unreasonable to think Alena could be working out of a deficient right from the start. And Kamila especially (but Anna as well) have PCS that aren't that far behind her and are climbing. (Anna's was almost the same by the end of last season and Anna is the 2x reigning Russian champion and her PCS are higher this year. Kamila also has recently unveiled her 3A and looks as strong as ever. And is the reigning junior champion of everything lol.) I don't think she can count on a PCS cushion like she could in the past. (Also Sasha, Liza, and Daria's PCS' are rising as well.)
So, in conclusion, yes I think a lot would have to happen for Alena to finish 6th and other skaters would have to skate to their potential and exceptions but it also wouldn't surprise me neither.