a story in the shape of a girl

It is a very rare group that can support two at once. Sires are not counted on to support fledglings. Rather, the community teaches a new fledgling based on cultural knowledge.

A family may approach a larger, established group with the request to turn one of theirs.

I have chosen to interpret Neanderthal language capabilities as existent, but utilized less than humans. They would come across as extremely terse, favoring demonstrations and body language above words.

Vampires would also serve as the main source of record keeping across generations. Without written language and with much less of a tradition of spoken language, vampires would serve as a repository of information across generations.

A lone vampire is considered a tragedy. To outlive your family is terrible. They might join another family, but there is a cultural expectation that they might also commit suicide.

Neanderthals are noted from genetic records as having females join other families while males stayed with their birth family. The cultural reasons behind this are lost to prehistory, so I have chosen to creatively interpret this as women leaving home at the cusp of adulthood to find a new group, as a reversal of commonly assumed human gender roles. They would take on the role we associate today with "young bucks". Possibility more sexually forward, possibly seen as braver than men.

Because of this, female vampires are more likely to find a new family than male vampires. It is expected that a female vampire may be part of multiple family groups before succumbing to grief or accident, while a male vampire is expected to die with their first family.

After all, a female vampire's first community that she took care of likely would not be the one she was born into. She would have experience in finding and joining a new family.

Men would be considered to be prone to grief, and so are not as heavily favored to become vampires. There are instances, though rare, of male vampires who's family have died becoming predatory towards those who killed them. It's considered a great tragedy, and any local vampires are called together to stop them. This is strongly associated with grief-stricken vampires striking out against homo sapien groups, but in practicality, this likely happens just as often against other Neanderthal groups.

This is one of the reasons women are favored for vampirism, since they are considered to be less prone to grief. Vampirism is not strictly segregated by gender, however. It's a trend rather than a rule. The choice of who to turn depends much more on the individual family that is considering having a member turned. The person would be selected from a relatively small group, so individual personality and skillset would be much more relevant. Gender would have an influence, but it would not be the deciding factor.

Denisovans populated islands much more than Neanderthals. There isn't any evidence of them traveling between islands, but it is entirely possible considering how little information we have about them. If vampires could not cross running water, then perhaps they would be unable to travel with their family to different islands. Considering Philippino vampire analogous stories, perhaps this plays into vampires being a danger rather than a member of the community.

Neanderthals would consider them to be stricken by grief, as that is how they characterize their own predatory vampires. Abandoned by their family and unable to travel island to island, Denisovan vampires would be vulnerable to starvation. Characterizing them as driven mad by grief would be an easy way to make sense of them.

All this to say, a Neanderthal vampire would be confused and horrified at the common perception of vampires today. A solitary, predatory figure who maintains secrecy would be repugnant to them.

Also, if a Neanderthal vampire did survive to today, she is more likely to be a woman.

The last Neanderthal vampire would call modern vampires grief-mad, comparing them to orphaned vampires of her own traditions, and vampires from Denisovan customs. This would not make sense to anyone but her anymore.

Perhaps she would blame herself for not teaching homo sapiens how to have vampire family members, and instead letting Denisovan customs be the dominant force.

After all, as a woman, it would be her duty to take on another family and carry on her traditions. A man might be forgiven for giving up out of grief, but she is supposed to be above that, even if no one else expects that anymore.

The last Neanderthal would never again be at full strength. Homo sapien blood would certainly feed her better than animal blood, but it is not the same. She would never again be fed by her people. She will never see them again.

Likely, she would end up adopting human families in central Asia, perhaps up into Russia. Rural, isolated families that would not expose her to the modern world. Perhaps she hibernated shortly after she lost the last of her people in Gibraltar. Perhaps she never knew they were there, and despaired too soon.

Either way, she has had almost 40,000 years of being weakened and lonely. Who is to say if she even remembers what it is like to be fed by members of her own species. Who can say how deep her grief runs.