I used to run a will-writing company, so here's my input:
An unwitnessed will is simply a totally meaningless piece of paper. The will MUST be signed AND witnessed. Further, it's vital that the witnesses actually SEE the testator sign. (They don't need to see the content of the will. Indeed, they don't even know that the document is a will but they MUST be present when it's signed. They CAN'T add their signatures later).
Beneficiaries under a will MUST NOT witness it. (If they do so the will remains valid except for the parts which leave something to them). Family member who AREN'T beneficiaries CAN be witnesses.
Witnesses DON'T need to be known to the testator. My own will was witnessed, by a couple of people I happened to be working with that day, on a Tesco car park! Your aunt could (for example) get a neighbour and the postman to witness her signature.
If your aunt dies without leaving a valid will, the laws relating to intestacy will apply. That
probably means that her daughter will get everything
https://www.gov.uk/inherits-someone-dies-without-will
but I'd still advise that a will should be written. (I told my own father that if, after his death, I found that he'd left everything to the cat's home I wouldn't be bothered. However if he died without leaving a will, even though I would get all of his estate under the laws of intestacy anyway, I'd be bloody annoyed because I'd have far more hassle to deal with!)
Your aunt's will doesn't need to be complex. The following would suffice:
"This is the last Will and Trestament of me, Agnes Aunt, of 42 Acacia Crescent, Sometown, in the County of Hereshire.
I appoint Norma Niece of 42 Acacia Crescent, Sometown, in the County of Hereshire and Another Relative of 23a The Grove, Othertown, in the County of Thereshire as executors of my estate.
I hereby revoke all former wills and testaments.
I leave my estate, in its entirety and wheresoever situate, to my daughter Norma Niece of 42 Acacia Crescent, Sometown, in the County of Hereshire.
In witness whereof I have here unto set my hand this twenty-third day of November two thousand and sixteen.
[Aunt's signature]
Signed by the above named testatrix Agnes Aunt as and for her last Will and Testament in the presence of us both present at the same time together who then at her request in her presence and in the presence of each other hereunto subscribed our names as witnesses
[Signatures of witnesses, with their names and addresses printed underneath]"