CI794 to CI57 isn't interline, I can't imagine why they would not do this for you. The call center should be able to tell you whether or not in principle they will do this. Another concern is that looking at FR24, CI794 is more often than not late into TPE, sometimes after10pm, so you probably want to be sure they will check through as if the flight gets in late you definitely won't have time to self-connect. Third, flights from Vietnam arrive into T1 at TPE and flights to Australia are out of T2 so you'd have to change terminals as well if re-checking in. All of these will be no issue if they are willing/able to check your bags through.