I'd wait until her heat. And if she's still not receptive, watch a bunch of videos of how male dogs initiate sex with female dogs. Things like panting, sniffing her pussy, licking the outside of her vulva, light playing like a dog would play with another dog, waiving your dick in her face, and being on all fours, might help turn her on. But if she says no. then listen to her. Some dogs like sex, and others don't. They sure aren't going to like it if you constantly force it on them.
My little girl dislikes sex for the most part, and the farthest I got with her on her last heat was fingering her, she enjoyed that well enough. And for such a little girl (35 lbs) she has a very roomy pussy! But as soon as I lined up with her to mate, she'd get all squirmy. As soon as she did, I let her go. After a few tries, I just let her be. I only tried one more time while she was in heat and the same thing happened. I haven't touched her that way since. I'll try on her next heat, and if the same thing happens, then so be it. The dog needs to be the ones who decides if they want to mate with you, not the other way around. The best you can do is try to get them horny.
My newfie on the other hand, is a freaking slut! lol