What would you do in my position?

She would bring my son his favourite biscuits. She knew exactly which yoghurt my daughter liked. My children loved going to her side of the house. I didn't see a problem with it. I told my husband, "At least the children have someone else who cares about them." He was happy. He would say, "See? This is how co-wives should behave." I agreed. Until my daughter changed. My daughter had always been attached to me. She used to sit in the kitchen while I cooked. She would tell me about school Then one evening, I made her favourite rice. She looked at the plate and said, "I don't want it." I asked why. She said, "Aunty said I shouldn't eat too much of your food." I froze. l asked, "Which aunty?" She mentioned my co-wife. I didn't confront her immediately. l asked my daughter what exactly had been said. She said, "She said you don't know how to cook healthy food and that I should eat what she gives me." I was hurt. But I still thought maybe my daughter had misunderstood. Children sometimes repeat things differently. So l let it go. A few days later, my son came home from her side carrying a new school bag. I asked him who bought it. He said, "Aunty." I thanked her. She smiled. "They are my children too." I appreciated the sentiment. But later that night, my son asked me, "Mummy, why don't you buy us nice things?" I was confused. I asked him, "What do you mean?" He said, "Aunty said you don't like spending money on us." That one hurt. Because my children knew how hard I worked to provide for them. I sat down with my son and explained that adults sometimes have different ways of showing love. I didn't say anything bad about his co-wife. I didn't want to put my children in the middle. But then something happened that I couldn't ignore. My daughter came home from school upset. She had forgotten her lunchbox. She told me her teacher had asked why she didn't bring the food she normally brought. I asked her what she meant. She said, "Aunty told me to take the food she packed because she said you would be too busy to prepare mine." I was shocked. I had prepared her lunch that morning. My daughter had simply refused to take it. That evening, I went to my co-wife. I didn't shout. I asked her calmly, "Please, I want to understand something. Why are you telling my children things about me?" She looked surprised. "What things?" I explained. She immediately became emotional. "Sister, I am only trying to help your children." I replied, "Helping them is not the problem." "Making them believe their mother doesn't care about them is the problem." She denied everything. Then she cried. My husband came in. Before I could explain properly, she told him I was angry because the children preferred spending time with her. He looked at me. "Is that what this is about?" I couldn't believe it. I told him, "No. This is about what she is telling the children." He asked her. And because there was no recording... No message... No written evidence... It became my word against hers. My daughter was too young to be dragged into an adult argument. So I stopped. I didn't accuse her again. Instead, I changed what I did. I became more present with my children. And I told my husband very clearly, "Nobody should use our children to compete with their mother." Then something happened that made me realize I wasn't imagining everything. One afternoon, my daughter came into my room crying "Mummy, please don't be angry with me." I asked why. "Aunty told me not to tell you that she bought me something." l asked, "Why would she tell you to hide something from me?" My daughter didn't know. That was the first time I became truly worried. Because buying my children gifts wasn't the issue but that they needed to keep secrets from their mother. I still haven't accused my co-wife of anything beyond what I can actually prove. Maybe she genuinely thinks she is helping. Maybe there is something deeper going on. I honestly don't know. And now I need advice. Should I confront her again? Or should I simply continue watching and documenting the things that happen without turning the children against her