While it is good that you are ready to move on to a new and promising relationship, it is apparent that your daughter is not quite ready. For a while to come, it is likely that your daughter will feel a strict allegiance to her biological parents because they are all she has known for most of her life. She will probably accept your new relationship eventually over time, but it is not something you can force. Time and patience are required.
You use the term “introduce” when referring to your boyfriend meeting your daughter. If she has not met this man yet, it might be wise to postpone the introduction. Right now your daughter needs to feel that she is a main priority in your life despite the changes your family has undergone due to the divorce.
Please remember that while you know she is your priority, she may not feel that way. From her perspective, she may feel like she is not as important as she once was. We can never assume that children accept and understand everything they see or are told. Many times kids' take on things is very different from what we see or think.
If she has met your boyfriend, try to keep her exposure to him neutral. Limit their time together until you and your boyfriend know that your relationship is progressing to a serious level. When you are all together, make sure the situation does not cause you to divide your attention between her and your boyfriend.
When your daughter seems receptive, let the time you spend together happen naturally. Don’t force activities. When she seems resistant, let her know that it is OK as well. You want to acknowledge her feelings but not cater to them. She has to know that while you love and care for her, you will not be manipulated by her behavior.
Often in divorce situations, when parents start to date again children feel like the absent, biological parent is being replaced. Assure your daughter that her father will always be her father whether he lives with her full-time or not. He will always love her and be part of her life. Your boyfriend is not a replacement for her father; no one could replace him. He is another adult who will love and care for her. You may have to explain this many times before she understands it or accepts it.
Communication is vital. Keep talking with your daughter. How she views the divorce now at age 10 is different than how she viewed it when it first happened at age 7. Her friends may also be sharing their own stories of divorce with her. Even if the situations are different, your daughter could be applying a friend’s divorce circumstances to her own family’s situation.
Spend time talking with your daughter when your boyfriend is not present. Keep reminding her that he is not taking her dad’s place, nor is he taking you away from her. Neither is happening now or in the future.
If you and your ex-husband manage a positive co-parenting relationship, you could enlist his help as well. Perhaps he has started a new relationship too. He could have similar conversations with your daughter to reinforce what you have discussed with her. She may come to understand that all will be well if both of you are doing the same thing.