Llinor shaves her head for Pobol y Cwm role.
In tonight's episode viewers see Gwyneth ask hairdresser friend Julie to cut her hair short and then beg her to take it all off.
Gwyneth found a lump in her breast in last year's Christmas Day episode and has been undergoing chemotherapy ever since.
Pobol bosses suggested Llinor wore a special skullcap in the show.
But the 30-year-old actress insisted on having her long curly hair shaved off for real to better understand her character's plight.
``Many people, both men and women, see their hair as a very important part of their appearance,'' said Crymych-born Llinor.
``When they told me what was going to happen to Gwyneth, I decided there and then to cut my hair short. ``After all, it's a soap series' duty to maintain credibility and depict things as they are in true life.''
Llinor has also got together a team from Pobol y Cwm to run the Race for Life this June and is busy collecting sponsorship money in aid of Cancer Research UK
Pobol y Cwm star Llinor ap Gwynedd has had her hair shaved off