Yes, but this sentence would most likely be used as an introduction (Oh, hi Mark here is my wife Rania). If you wanted to say My wife is Rania, most would add ' هِيَ ' which means she is. If you wanted to, for example, identify your wife from a list of names, you would say: "زَوْجَتي هِيَ رانْيا", which translates to My wife, she is Rania.
I agree that the version with هي makes it clearer. But without further context provided, زوجتي رانيا is equally translatable to "my wife is Rania" which should be accepted in my opinion. Duolingo's policy with other languages is that all possible translations are accepted and not only the most likely ones.