I think it probably is too good to be true. I think her recovery time will be mainly related to the severity of the injury.
Having searched for HEM on the internet it talks about exercises to strengthen and reduce scar tissue. That's all good, but if there's ligament damage (which is what a sprained ankle is) then that will take the normal approximate 6 weeks to heal.
I would take it each day at a time and do all the normal things the doctors and PT recommend for a sprained ankle. If it's a mild sprain you never know, she might be comfortable in her boots for the competition or else she pulls out. There'll be another one.
As for synchro tryouts, I'm sure if you contact the club and explain the situation they would try to accommodate. She's hardly going to skate her best on a sprained ankle.