I’m getting really into Helena Bertinelli for the first time while trying to make a Batman comics AU timeline involving her and… I’m SO confused about her backstory. Cry for Blood is my main source for her characterizion and story, and I understand that this timeline is a retcon of the previous one where she was nineteen instead of eight during her family’s massacre, but is Huntress: Year One the same timeline? Or are the original Huntress run, Year One and Cry for Blood all different versions of events?
Specifically, what exactly happened between her watching her family die and operating as the Huntress in Gotham? How long did she live in Sicily and Switzerland? How much time did she actually spend in Gotham to be inspired by Batman? ‘Cause it doesn’t seem like a lot. When were her uncle and cousin arrested? Why did they go back to Gotham at all after the massacre of their relatives? How did she go from being okay with the Mafia to its greatest enemy while raised by them? Or was that after the arrests, when she was on her own? Is there a good, logical, well-written canon consensus on these details or would I have better luck making something up myself?
Helena Bertinelli has had many a retcon to her origin over the years. Direct answers can be hard to find in characters that have been written many times by many different authors. To go over a general overview of post-crisis:
As you mention, her original introduction to post-crisis comics in The Huntress (1989) does have her being a young adult when her family was massacred. It also has her being based out of New York. While I quite like this series and origin for her, most of the series has been completely reconnected out of existence.
When she was re-introduced as a Bat comic supporting character in Detective Comics #652 and #653, she was retconned to be from Gotham instead of New York, though a number of elements of her original backstory, including the fact that she had been an adult when the massacre happened remained the same.
Batman/Huntress: Cry for Blood, was a major retcon for her and lays out a whole new character history. If you want to build an AU timeline, you'll be just fine using that as a source. That origin introduced her being 8 when her family was massacred, the same age as Bruce, a retcon that has carried forward.
Huntress: Year One is another retelling of her origin, which is primarily building off of her origin in Cry for Blood, only expanding it more and digging into, well, her first year as the Huntress. She's still 8 here when she's orphaned. There are some changes to the timeline that are made. This also removes her taking influence from Batman to become a vigilante.
To answer some of your questions:
Pre-Cry for Blood
In Huntress '89, very soon after the massacre (probably no more than a week), she goes with her bodygaurd, tony, to be trained. It is unclear how long she spends training, but it likely isn't very long. She is not inspired by Batman to become a vigilante. She was kept largely separate from the family business as a child and primarily sets out as the Huntress to avenge her family's death. After that's done, she finds that she has trouble living a normal life and continues to help people, growing disillusioned with her father. She does not really crusade against the mob until she's reintroduced in Gotham comics. There it's implied to be a mixture of desire for personal revenge for what caused her family's death, familiarity, and personal distaste for what they do, from what I recall.
Cry for Blood
After her family is massacred, Helena spends 7 years living with the Asaros in Sicily. She is training under Sal from age 11-15. When she's 15, her uncle and cousin arrested and she goes to boarding school in Switzerland where she begins to understand the truth of the mafia and hate them. At 16, the Cassemotos bring her back to Gotham for Christmas, thinking it's safe which is when she sees Batman and is inspired. She then spends probably the next 4-6 years planning and preparing before she finally returns to Gotham to get her revenge and fight against the mob. (It isn't specifiied by she finished boarding school and enrolls in university in Palermo).
Huntress: Year One
The timeline is largely the same when it comes to the massacre and the Asaro's arrest. They were arrested about 5 years before her 21st birthday, placing her at 15-16. She then goes to school in switzerland before returning to Sicily. Unlike in Cry for Blood, Helena hates the mob from the start from the violence she has continually see them commit. From what I remember, university is never mentioned. She does not return to Gotham before becoming the Huntress, and comes up with the idea and costume separately. She also does not want to return to Gotham, but eventually needs to return to pursue her vengeance.
Conclusion:
I personally mix and match elements as I please when writing Helena's origin. If you want a single comic as a touch-point, I would just stick with Cry for Blood as it's the strongest in opinion. I think that's also the one people are more likely to know. You won't go wrong using that as your base, and filling in the gaps as needed.