Unfortunately, you can't force your baby to sleep. There are different things that they go through as they grow that affect their sleep patterns...growth spurts, separation anxiety, medical reasons, teething, bedroom temperature...you get the idea. First check to make sure that something that can be easily fixed isn't what's causing your baby to wake up. Like the temperature in the bedroom or scratchy pj's, noise. Blah blah blah. If it's nothing like that then maybe it's just because she's become used to only falling asleep one way. If that's the case try different ways of putting her to bed so that she can fall asleep in a variety of ways. Since you always rock her, try singing instead or try putting her down when she's still awake but almost sleeping so that she can learn to fall asleep on her own. It's going to be rough transitioning but it's worth it. If nothing works, then just prepare to be tired for a little while. It may just be a phase that she's going through.

*edited to add* just thought of a white noise machine. a friend of mine swears by it.

There are so many reasons why babies go through stages where they wake up. I think it's important when she wakes up to keep her enviroment stimulus free. Keep the lights low, don't talk or play with her. If she's fussy or acts scared reassure her, but try to do so without a lot of drama. If she learns that when she wakes up it's play time, you'll be in for a long road of this.

I rock my son to sleep every night. He is able to go to sleep on his own, because he does it at nap time. I love it and it's special time that we share. It won't be long before he won't want that anymore and I'm going to cherish every moment he does.