Further explanation of the ruling which says that it is permissible for kaafir women to see Muslim women without hijaab
Question

                you said kaafir women can see you without hijaab,i'm not convinced since you mentioned only 1 hadeeth of aaishah (r.a)revealing herself to a jew.can you explain some more cause my inlaws are kaafirs?
Praise be to Allah.Your 
    keenness to be modest in dress in front of kaafir women is something to be 
    commended and appreciated, especially at a time when there is so little 
    modesty and gheerah (protective jealousy – of men over their womenfolk) is 
    so weak. 
With regard 
    to the issue of kaafir women seeing what ordinarily appears of the Muslim 
    woman, this is an issue concerning which the Muslim scholars of the past and 
    present have differed. Under Question no. 2198 
    you will find a summary of what the scholars have said and the evidence for 
    each opinion. You will notice that those who say that it is permissible for 
    a kaafir woman to see a Muslim woman without hijaab have more than one piece 
    of evidence to support their view. 
But it is 
    worth pointing out the following: 
1 – If a 
    Muslim woman has saheeh evidence concerning some matter of sharee’ah, and 
    the evidence is clear and the meaning is apparent, then she should follow 
    it; it is not essential to have two or more pieces of evidence for every 
    issue. 
2 – If the 
    kaafir woman is not trustworthy and there is the fear that she may describe 
    the Muslim woman to her husband or say something that will harm her honour, 
    then the Muslim woman has to beware of her by wearing hijaab, not mixing 
    with her and so on. 
3 – The view 
    that Muslim women should wear hijaab in front of kaafir women is a valid 
    opinion and is correct to some extent. Many of the salaf (first generations 
    of Islam) expressed this view. So if a Muslim woman wants to be on the safe 
    side regarding her religion and follow this opinion, she may do that. It is 
    hoped that her caution and her keenness to avoid something doubtful will 
    bring good results. But she should not denounce those who differ from her in 
    that, so long as the matter is subject to ijtihaad and differences of 
    scholarly opinion, especially when there is no fear of fitnah from the 
    kaafir women. 
4 – Women 
    should not go too far in uncovering in front of their mahrams or Muslim 
    women, let alone in front of kaafir women. Rather they should not show any 
    more than that which ordinarily appears, namely the hands, calves, neck and 
    hair. Modesty is a branch of faith. You will find more details and further 
    explanation under Question no. 6596. And Allaah 
    knows best. 
May Allaah 
    bless our Prophet Muhammad.