I'm not sure if my opinion is warranted, since I am not a divorcee, but I thought maybe I could shed a little light on the situation from your daughter's perspective, since I am the product of divorced parents.

Byzantine is right when he says that your daughter is the one who suffers when you or your wife keep her from seeing one another. I can't imagine how difficult it must be for you, since I have worried about how I would handle a breakup with my boyfriend now that we have a child together. It is hard not to fall into the trap of using the child to get to the other person, and you might be surprised at how much your daughter understands that (even if she is very young). I ended up being a go-between therapist for both my parents, constantly hearing how the other parent didn't measure up. If you can find the emotional strength, please try not to bad mouth your wife when your daughter is around. Even if your wife decides to try and "turn your daughter against you", so to speak, she will never be able to. Daughters have deep admiration for their fathers and as long as you love her and support her, she will never turn her back on you. I'm just saying that from personal experience. Children have unconditional love, so all that she will want is for the two of you to be happy and, most of all, to know that you both still love her. If she is being used, she will sense it, and she will be confused as to how much you both still love her. Try to be sensitive to that, if you are able.

I'm glad that you are in therapy. I think that will help you have a better relationship with your daughter when the storm of the separation blows over. It sounds like you already know that what the two of you are doing is wrong and is hurting your daughter immensely. The next time you feel the urge to keep her away from your wife out of resentment or hurt, remember how your daughter has the right to love BOTH of you, and how much you are hurting her with your actions.

The good news is, no matter what mistakes you've made so far in handling your emotions, your daughter will always forgive you and love you! :-) I am only speaking from personal experience, and I agree with Byzantine that my opinion or perspective (which is uniquely mine and may not even really apply to you) is worth much less than that of your therapist. Keep trying your best every day to handle each situation with dignity and grace. Make sure you take some time for you so that you have as much mental space and strength as you can to handle difficult discussions with your wife, or actions that she takes with your daughter that are irresponsible or hurtful. I think this will help you keep sound judgments, and hopefully prevent taking out your frustrations on your daughter.

Good luck! I'll keep you and your daughter in my thoughts. This, too, shall pass...