My main question was related towards figuring out if I should keep pursuing it, and try to change their minds, or if I should respect their wishes ... the difficulty of this situation is compounded, because I'm angry with her.

As the first step I would recommend to stop being angry with her.

Also keep in mind that for a true-believer Christian cryonics is basically trying to cheat oneself out of heaven -- not a very appealing idea :-/