Well, maybe "writing talent" is a debatable point -- even though her published diary contained very inspired thoughts and passages...
There was a rather quiet but decades long debate in literary academic circles over just how much of the diaries were Frank's work and just how much of the diaries were the work of her father Otto and inquiries into the same. Because the Frank diary is often the target of Holocaust denying assholes of all stripes, the debate and inquiries were necessarily muted.
Otto's death and the subsequent release of the original materials to a Dutch organization settled the issue somewhat. IIRC a conversation I had with a friend who taught at Brown, she informed me that Frank had two diaries: an original one with all the banal teenage girl stuff and another which she edited and expanded on from the first in the hopes it would be published post-war. Otto then further edited the second version.
The Frank diary is powerful, in part because we know the ending in advance and in part because Frank herself composed powerful passages. Because Frank began the editing process herself, she was able to rewrite certain earlier portions several times for better effect and we know little about whether she had help or read passages to others for advice.
Of course Otto later edited other passages for the same reason.
That's not to say she couldn't develop this capacity, though I admit now she was far from destined to do so. Would you admit she had the "inspiration" (or spark, or whatever you want to call it) to be a writer?
I'm not saying she could never do so. I'm just playing the odds. How many "one hit wonders" have there been in the world of literature? For instance, Harper Lee had only one
To Kill A Mocking Bird in her.
Could Franks make the leap from an writing intense personal memoir of a horrific period in human history from a teenage perspective to writing about other subjects from an adult perspective? We must admit that much of the power of her diary flows directly from it's setting and not directly from Frank's abilities as a writer.
Sadly, I think the odds are very much against her.