She should be tried in Syria, it's where her crime was committed. I get why some people disagree, because let's be honest, the courts in Syria don't live up to any acceptable standard. But if you travel from a rich country with a functioning judicial system to a poor one with a dysfunctional one to commit crimes there, that's the risk you're taking.
Perhaps, but a government still has an obligation to try to ensure fair treatment of its citizens abroad. Otherwise, that would open the door for every despot to take political hostages at will and prosecute them for made-up crimes.
As for the OP's question, there's an additional complication in that Shamima Begum is claimed to have been brought to Syria by a Canadian intelligence agent, meaning she didn't go there on her own free will. If true, then repatriation to face trial in her country of citizenship should be the only reasonable course of action.
Revoking citizenship should never be an option, unless it was obtained by fraud. Even traitors cannot have their citizenship revoked, since there still needs to be a legal basis to try them.
