Christina's death was detailed in a recent GoFundMe made by her family, who say they got a call last week from another family member, frantically screaming that she was dying ... something they say "instantly shattered our world."

They quickly arrived at the hospital where they were told her health went in a steep decline after suffering a cardiac arrest and she didn't make it. Her family says the death's being investigated as a potential homicide -- related to a "medical procedure that took a turn for the worse."

There have been reports that the procedure Christina was undergoing involved plastic surgery ... but the family says they aren't going into more detail at this time.

As for the fundraiser, they're asking people to help reach their $40K goal to go towards Christina's memorial.

For those unaware, the model -- who also went by Ashten G -- didn't just garner a ton of followers on OnlyFans, but also had over 600K on IG at the time of her death ... getting a ton of attention for bearing a striking resemblance to Kim K.

Christina was 34.