A Christian Wife Having a Cross in the House
26-9-2019 | IslamWeb
Question:
Asslamualaikum. A Muslim has a wife who is Christian. She has a cross in her room. Can he allow that?
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
A non-Muslim wife from the People of the Book (i.e. Jews and Christians) has the right to practice her religion and perform her religious rituals. Her Muslim husband does not have the right to deny her such a right, as long as it does not entail undermining his own rights over her as a husband.
Imam Ahmad 
was once asked: "Does the Muslim husband have the right to prevent his Christian wife from bringing a cross in his house?" He replied: “He should command her not to do so, but cannot force her not to bring it in." [End of quote]
However, you should know that this only applies to a cross, but not a crucifix as it has a depiction of 'Eeasa (Jesus) 
. It is not permissible allow such statues to enter into the house because, in principle, possessing these statues is forbidden, and they prevent the angels from entering the house. To sum up, you may allow her to bring a cross into the house but not a crucifix.
Lastly, it should be noted that it is better for a Muslim man to marry a righteous Muslim woman who would be in agreement with him on matters of the religion and who would help him adhere to Islam.
For more benefit, please refer to Fatwa 90298.
Allah Knows best.