I have met at least 10 women who claimed they were Maria in previous life (the one from the Bible)
And also about 3 who claimed they were Jesus in a previous life
So this kid seems quite humble ... just princess Diana.
If you look at the specifics of Diana's death, it seems plausible. Generally with people who know about it and understand it, they go for a location, or more likely a family. They sit on the astral and wait for an opportunity that suits them, a place to undergo karma in a logical way. For those who don't believe, the astral is just a strange place. Then there are those like Diana, who lose the physical body suddenly with no time to prepare or to mentally adjust. (Alcoholics and drug addicts, anyone who dies in a stupor, are another category like that ... that's why hindus and others wish to transition in a clear state of mind) Certainly it seems she had desires to 'get away from it all' and Australia seems like a logical place to get as far a way from Britain as possible. Wishing to be male seems logical as well. But it seems more likely it would be 'pot-luck' random because of the suddenness of the death.
As for claims like you mention ... well, yeah, people have daydreams. But when a 2 year old (or younger) babbles somewhat coherently about some other place or stuff ... personally I take that a way more seriously than some adult full of ego, and transferring that to the soul nature.
Hopefully this kid will forget about it real soon, and there won't be much media. After all, that soul wished to get away from that, must be some lingering desire I suppose.
(It's raining here, and I'm taking the day off from landscaping, so am yapping too much.)