He is not sure about the meat that his mother buys
Question

                My question is: my wife and I are Muslims and we try to eat halaal meat as much as possible. But my mother is not Muslim and she buys meat from stores that do not sell halaal meat and cooks it. Is it haraam to eat the meat that she cooks for us?? Please note that she does that with a good intention. Is there any harm in refusing to eat the food she offers to us? What is the ruling on that? May Allah reward you with good.
Praise be to Allah.
    Firstly: 

    If the meat has been slaughtered by one of the People of the 
    Book (a Jew or a Christian) and we do not know the method of slaughter, but 
    most people in the country kill meat by means of electric shock or by 
    slaughtering it for someone or something other than Allah, it is not 
    permissible to eat that meat, on the basis of what is usually the case. The 
    same applies if one is not sure whether the meat was slaughtered properly or 
    killed by means of electric shock. That is because of the report narrated by 
    al-Bukhaari (5485) and Muslim (1929) from ‘Adiyy ibn Haatim (may Allah be 
    pleased with him) from the Prophet (blessings and peace of Allah be upon 
    him) who said: “If you release your (hunting) dog and say the name of Allah, 
    and (the dog) catches (the game) and kills it, then eat, but if (the dog) 
    ate (some of it), then do not eat, because he only caught it for himself. If 
    another dog joins him over whom the name of Allah was not mentioned, and 
    they caught it and ate from it, do not eat, for you do not know which of 
    them killed it. If you shoot an arrow and you find (the game) after one or 
    two days with nothing but the mark of your arrow on it, then eat, but if it 
    fell into water, do not eat it.” 

    According to a report narrated by Muslim: “When you shoot 
    your arrow, mention the name of Allah. Then if you find it (the game) dead 
    then eat, unless you find that it has fallen into water, in which case you 
    cannot know whether it was the water that killed it, or your arrow.” 

    The Prophet (blessings and peace of Allah be upon him) 
    forbade eating if there is any uncertainty as to whether the meat was 
    slaughtered properly in accordance with sharee‘ah because of the hunting dog 
    being joined by another dog, or because of the target animal falling into 
    water and the possibility that it died by drowning. 

    Al-Nawawi (may Allah have mercy on him) said in Sharh 
    Muslim: The words of the Prophet (blessings and peace of Allah be upon 
    him): “If you find with your dog another dog and it joined in killing (the 
    game), Do not eat because you do not know which of them killed it.” This 
    states an important principle, which is that if there is any doubt as to 
    whether the animal was slaughtered in the permissible manner, it is not 
    halaal, because the basic principle is that it is haraam. This is a point on 
    which there is no difference of scholarly opinion. End quote. 

    Al-Haafiz Ibn Hajar said in Fath al-Baari: The words 
    “if it fell into the water, do not eat it” – the reason for the prohibition 
    on eating it is to be taken from the phrase above, because in that case 
    there is doubt as to whether it was killed by the arrow or by drowning in 
    water. If it is established that the arrow struck it and it died, and it did 
    not fall into the water until after it was killed by the arrow, then it is 
    permissible to eat it. al-Nawawi said in Sharh Muslim: If the game is 
    found in the water, drowned, it is haraam according to consensus. End quote. 
    al-Raafi‘i said that if he reaches it in time (before it dies) and cuts its 
    throat for example, then he has slaughtered it in the proper manner. His 
    opinion is supported by the report narrated by Muslim, “you cannot know 
    whether it was the water that killed it, or your arrow.” This indicates that 
    if he knows that his arrow is what killed it, then it is permissible. End 
    quote. 

    For more information please see the answer to question no.
    10339. 

    Secondly: 

    If your mother or someone else brings haraam meat, it is not 
    permissible to eat it, because Allah, may He be exalted says (interpretation 
    of the meaning): 

    “Forbidden to you (for food) are: Al-Maitah (the dead 
    animals - cattle - beast not slaughtered), blood, the flesh of swine, and 
    that on which Allâh’s Name has not been mentioned while slaughtering, (that 
    which has been slaughtered as a sacrifice for others than Allâh, or has been 
    slaughtered for idols) and that which has been killed by strangling, or by a 
    violent blow, or by a headlong fall, or by the goring of horns - and that 
    which has been (partly) eaten by a wild animal - unless you are able to 
    slaughter it (before its death) - and that which is sacrificed (slaughtered) 
    on An-Nusub (stone altars). (Forbidden) also is to use arrows seeking luck 
    or decision; (all) that is Fisqun (disobedience of Allâh and sin).”

    [al-Maa’idah 5:3]. 

    You have to be gentle and polite when explaining why you do 
    not want to eat this meat, and try to make your mother happy by eating other 
    food that she offers; bring her some halaal meat to cook when you are there 
    and try to convince her of the importance and benefits of eating halaal meat 
    and the harmful effects of eating meat that was not slaughtered in the 
    proper shar‘i manner. This is due to the rights that she has of respect and 
    kind treatment. 

    See also the answer to question no.
    172

    And Allah knows best.