Accepting money from kaafirs
Question

                My wife who is a christian inherited some money. Iam a muslim.I would like to know if I'm allowed to take any of that money and spend it since Iam not the one who  inherited it and since it's her money now and she is my wife .

Also if she leaves her assets for me in a will incase she passes away before me,would I be intitled to her assets ?.
Praise be to Allah.
    1 – There is no reason why you should not take from the money 
    that your wife has inherited, on condition that that should be with her 
    consent. 

    Allaah says (interpretation of the meaning): 

    “but if they, of their own good pleasure, remit any part 
    of it to you, take it, and enjoy it without fear of any harm (as Allaah has 
    made it lawful).”

    [al-Nisa’ 4:4]

    Al-Qurtubi (may Allaah have mercy on him) said: 

    The phrase “but if they, of their 
    own good pleasure, remit any part of it to you, take it, and enjoy it 
    without fear of any harm” is addressed to 
    husbands, and indicates that it is permissible for a woman to give her mahr 
    as a gift to her husband, whether she was a virgin or previously married. 
    This is the opinion of the majority of fuqaha’… The scholars are agreed that 
    if a woman who is in control of her own affairs gives her mahr to her 
    husband, that is a valid transaction and she cannot take it back.  

    Tafseer al-Qurtubi, 5/24, 25 
In general, if a kaafir 
    gives something to a Muslim “of his own good pleasure”, there is nothing 
    wrong with accepting it. 

    The Prophet  (peace and blessings of Allaah be upon him) 
    ate with the Jews. (Narrated by al-Bukhaari, 2424; Muslim, 4060) 

    The king of Aylah – a land on the seacoast – who was a kaafir, 
    gave him a gift of a white mule and a cloak. (Narrated by al-Bukhaari, 1411; 
    Muslim, 1392). 

    The Negus paid the mahr of Umm Habeebah on his behalf, and he 
    was a kaafir. 

    It was narrated from Umm Habeebah that the Messenger of 
    Allaah  (peace and blessings of Allaah be upon him) proposed marriage to 
    her when she was in the land of Ethiopia. The Negus married her to the 
    Prophet  (peace and blessings of Allaah be upon him), giving her on his 
    behalf her a mahr of four thousand dirhams, and prepared her trousseau, and 
    he sent her (to the Prophet  (peace and blessings of Allaah be upon 
    him)) with Shurahbeel ibn Hasanah. The Messenger of Allaah  (peace and 
    blessings of Allaah be upon him) did not send anything to her. The mahr of 
    his wives was four hundred dirhams. 

    (Narrated by al-Nasaa’i, 3350; Abu Dawood, 2086; al-Haakim, 
    2/181. al-Haakim classed it as saheeh and al-Dhahabi agreed with him). 

    And there are many other similar incidents. 

    2 – If she wills her possessions to you, and she was 
    following her own religion before she died, it is also permissible for you 
    to take these possessions, because a will is different from inheritance. But 
    if she did not make a will and died, then it is not permissible for you to 
    inherit anything from her. The Prophet  (peace and blessings of Allaah 
    be upon him) said: “The Muslim does not inherit from a kaafir and the kaafir 
    does not inherit from a Muslim.” (Narrated by al-Bukhaari, 6383; Muslim, 
    1614). 

    Imam Ibn ‘Abd al-Barr (may Allaah have mercy on him) said: 
It is proven from the 
    narrations of the trustworthy imaams that the Prophet  (peace and 
    blessings of Allaah be upon him) said, “The Muslim does not inherit from the 
    kaafir.” So everyone who goes against that, this hadeeth is evidence against 
    him. This is the view of  all the Sahaabah, Taabi’een and fuqaha’ of various 
    regions such as Maalik, al-Layth, al-Thawri, al-Awzaa’i, Abu Haneefah, al-Shaafa’i 
    and all the scholars of hadeeth who spoke on matters of fiqh, that a Muslim 
    should not inherit from a kaafir and a kaafir should not inherit from a 
    Muslim, following this hadeeth. And Allaah is the Source of strength. 

    Al-Tamheed, 9/164

    And Allaah knows best.