The Daily Star claim and its proof
There doesn't seem to be any evidence for the claim. It seems that the Daily Star went to three people who have some academic background, but whose focus is the media, and asked them their opinions on women, short hair, and sex. They found two that agree with their theory, and one that disagrees.
The Daily Star article is not a reaction to research or new discoveries in any way or form.
The original Daily Star article can be found here. The article isn't very in-depth, but it seems that the experts giving this theory "scientific backing" are Dr Pam Spurr and Anjula Mutanda.
Spurrs company describes her as "an award-winning radio presenter, agony aunt, relationship, sex and behavior expert, and life coach". She does have a doctorate in psychology, but here focus isn't research but media. Her take on the topic is:
The woman who no longer wants sex uses a haircut to show she’s reclaiming power in the bedroom. For women, hair is a reflection of the person, of her moods and her self-esteem.
That seems to be it. There are no articles that contain more context to that quote, and no article cites any papers she may have published on the topic; likely because no such papers or research exists. Dr Spurr also does not explain what "reclaiming power in the bedroom" has to do with "no longer [wanting] sex".
Mutanda is also more of a media expert. Her take on this is:
Cave paintings celebrated long-haired women – the longer the hair the more fertile and, therefore, desirable she was.
And again, this seems to be it. She doesn't say which research she references, which cave paintings are meant, how she knows from these paintings which women where desirable, or how it has anything to do with todays women and their short hair and sex drive (evolutionary psychology is often criticized as a discipline itself, but Mutanda doesn't even try to make a reasonable connection here [if indeed she wanted to make the connection and not the Daily Star]).
The Daily Star also asked a third person, Judy James, who is a "body language/behaviour [expert] with a high tv/radio profile". Here take:
The only thing it symbolizes these days is the shutting off of childhood. In terms of sex, I would argue it has the opposite effect.
And once again, this is it. James doesn't back it up by referencing any research.