It's likely your 7yo doesn't want you or bio dad to "ever get married" because she still has hopes of the two of you getting back together. How long have you been divorced?

Looking back, I should have seen the warning signs for SD11. When she was 5 she would bang on the kitchen table and chant "break up, break up." DH always thought it was BMs antics. Her parents had been divorced since she was 1 y/o. She doesn't even remember them being together. Yet she balled her eyes out on our wedding day. It's like she has been "mourning a loss" of DH and the thought that BM would get back together. A nail in the coffin so to speak. I think the finality of it is what COD have a difficult time with. 

Sidenote: That's why I have always thought when parents get divorced, they should NOT still be playing happy family. Going to movies, out to dinner, trips, etc. I think BPs have good intentions, but all it does it set up kids for disappointment. IMHO, that's why all co-parents should have healthy boundaries. 

Your child does not get to dictate your life, you are allowed to move on and have a happy relationship.

Always listen to your child when she confides in you, and make sure she always feels safe to do so. It is your job to protect her for any harm, but it isn't your job to stop living until she is an adult. 

Back the truck up a little bit.

Would you let a 7 year old make any other big life decisions for you or herself?  She likely would eat sweets and chicken nuggets for every meal if you let her make that decision.. lol.

A 7 year old should not have the power to make your dating decisions for you.  Neither does your EX and if your ex is putting ideas in her head.. you need to be the balance voice to let her know that her "happy family fantasy" of you and your EX getting back together is NOT going to work.. he will always be her daddy.. but you will not be his wife.

By asking her opinion.. you are giving her the misguided idea that this is a choice she gets to make.  Don't get me wrong, you can ask if she LIKES him.. if he is a fun person to be around... and listen if she says things that worry you from her.  But, waiting for her to greenlight your relationship is really giving her power she should never have.  It's not her choice to make.. it's yours.. and it's up to YOU to see whether he is a good person to have in your life and to have in your daughters.  Look for red flags of course.. be sure he is a good partner and one that will be supportive of your role as her mother.. but don't let her make this decision.

Kids are inherently selfish.. she will likely "never" want you to be with anyone.. if you pose it to her as if this is her option.  But, if you insist that she be respectful of your relationship.. and of your partner... and keep an open mind to that..that is what you need to have happen.

Now, of course if you have had a particularly traumatic break from your EX.. abuse.. substance abuse etc.. she may need counseling.. and you probably need to make sure you aren't jumping into a relationship too fast.. but again.. this is an adult decision.. not a child's

You are the parent, and DD is the child.  I agree with others that said you are giving her too much power.  I'd like to add that I hope she is not the one running your household.  The way you are parenting is typical of many of the permissive BPs we have on this site.  They let the child run all over everyone so as not to displease the poopsie.

Does your boyfriend have kids that are mean to your kid?

While I don't think kids should run things, I also don't believe in just forging ahead, kids feelings be damned. I think you need to get to the bottom of your daughter's thought process. Is she worried about being left out? Does she have hopes of you and her dad getting back together? You are going to have to find out what her fears about it are and find a way to relieve them.

In your other post, you talk about having a baby. I think there's some things to work out before that!

You should definitely listen to your child, but for information. Not instructions. Are her needs being met? Is she safe and secure in this situation? Kids don't know what's best for them at that age. You have to make the decisions based on the information you have.