...the main question being, why did Alissa's PCSs shoot up so miraculously between her short program (which was good) and her long program (which was bad)?
In the short program, Alissa had total PCS of 27.77 -- an average of 6.94 for each component, before factoring. This is not too far off Rachael's score of 26.17, an average of 6.54. (Mirai and Ashley, down in 6th and 12th

places because of mistakes on jumps, had PCSs of 26.62 and 25.66 respectively.)
Alissa's big lead over Rachael in the short program came on GOEs on elements, where Alissa had positive GOEs across the board and Rachael's were almost all 0's.
But then in the long, Alissa's PCS shot up to a whopping 60.63 (average 7.58) -- just what she needed to make up for lower TES and lower GOEs on botched elements and keep her in third place behind Ashley and Rachael in the LP, and first overall.
So the question is, was Alissa's long program so much better than her short that she deserved a raise from under 7.00 to over 7.50 in average PCS?
To further compare apples to apples, double the PCSs for the SP.
Rachael: SP 52.34, LP 53.31
Alissa: SP 55.54, LP 60.63