Is it allowed for women to remove the cloth from shoulder & neck in front of women at the beauty parlour , if we want to do facial ( beauty treatment ) , then they ask to change dress and wear a special gown that shows the top of the body i.e. neck , shoulder , a part of chest .
In the name of Allah, the most Beneficent, the most Merciful.
The awra of a woman in front of fellow Muslim women is from the navel up to and including the knees. (Hidayah p.461 v.4)
The awra of a Muslim woman in front of a non Muslim woman is like that of a non Muslim man, i.e. the whole body besides the hands, face and the feet. (Raddul Muhtar p.534 v.9) However, scholars have said if this is not possible to do then one can expose some parts of their body.
In conclusion to your question, it is advisable and preferable to cover your whole including the area between the neck and shoulder. If your neck and shoulder is exposed then it will be considered permissible in front of Muslim women and according to the second opinion in front of non Muslim women.
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham