This is a tough situation emotions ar involved and in reality this is a situation you cannot win.
If you convert then for the rest of your life you will be controlled by a faith that limits life and involves itself in every aspect of your life. It does not hold back from telling you what is acceptable between husband and wife, how much contact you should have with non believers, what career you can have, what you should read, watch and listen to. You will be unable to celebrate normal life events and you will be distanced from every person who does not share your beliefs. All this for a woman who will be more loyal to the congregation than to you, someone who can only give you conditional love and who will walk away from the relationship if you no longer follow her beliefs.
If you do not convert you will find that your relationship is constantly undermined by her faith. As you will be deemed a worldly person your opinion counts for little and the elders will have more influence over her than you will. It will not be an equal relationship. You will constantly be compromising for her faith as witnesses are taught that they must be loyal to Jehovah above personal relationships. Witness family life is disfunctional.
She cannot invest as much in this relationship as you can. I would ask her if she intends to remain a witness and if she does then walk away. It will be painful but in the long term you have the opportunity to meet someone who can offer you a committed relationship. You cannot change her if this is what she wants.