All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
This woman is obliged to accept when you call her to bed even if she has no desire for sexual intercourse unless she is harmed by doing so. If the wife has no desire for intercourse, this does not necessarily mean that the husband has no desire.
If you are able to be just between two wives, then you may marry a second wife who will help you maintain your chastity, and Allaah may bless you from her with pious progeny. For more benefit in this regard, please refer to Fatwa 83574, and for knowing the disadvantages of marrying women of the book, please refer to Fataawa 84724 and 89418.
Finally, it should be noted that you should endeavor to call this woman to Islam and show her the merits of this religion, especially by treating her with kindness and so forth.
For more benefit on calling the Christians to Islam, please refer to Fataawa 82164 and 84349, and for introducing Islam, please refer to Fataawa 86091 and 81979.
Allaah Knows best.