It is extremely unlikely she's claiming to know that Russia threw the election to Trump.

She's claiming that Obama is boxing them in because if they object to the sanctions it might make people wonder if there was a quid pro quo. She's also saying that Obama might have further evidence on Russia and that he might be leading Trump into a trap (where Trump says nice things about Russia and then, bam!, Obama releases some direct evidence).

She's not claiming in this email that she knows Russia helped them win the election.