i'm not one to force sleep, so my suggestions might be out of line for you, but you may as well have them to pick from!
first of all, if she was 13 weeks premature, she's really only 12-13 months old. and that's a big difference (12 months vs. 15 montsh) as far as sleeping goes.
the other thing i would say is that even if your routine says bed at 7:30 with bath and reading, etc, if she's too squirmy to listen, she's just getting more riled up, rather than relaxed, by these routines. maybe you could wait another 20-30 minutes before starting the routine if she's squirmy and doesn't want to relax as she used to? or look at the whole day - is it just bed time when she doesn't want to go down, or nap time too? maybe it's time to decrease a nap or push back bed time?
otherwise, i personally am totally against crying it out, it just feels wrong. and if rocking and reading has worked until now, why not keep doing it? i mean, why force your daughter to self-sooth before she's ready? she won't be a baby forever, and in the grand scheme of things, another year or two of reading and rocking her to sleep is only giving her more love, not hurting her in any way. she will self-sooth and put herself to sleep in her own time, and the longer you make yourself available to her the more securely she will actually feel about herself. psychology is strange that way! i think about it this way - it's hard to trust myself or feel safe if everyone around me says I'm not trust-worthy, that it isn't safe, and keeps leaving me in situations that both decrease my trust in them and my feeling of security. do you see what i mean?
if it's really important to you that she go to sleep on her own because of something else that's changing in your family situation, maybe you could try changing the routine so that it's more likely she'll fall asleep on her own... like, read to her in her bed (or your bed) instead of the rocker. wait until a little later so she'll be more apt to fall asleep while you read. read an extra book. just lay with her. maybe think in terms of sections of bed time or steps -- the bath, the pjs, the reading, the rocking, the falling asleep. if the end goal is getting her to fall asleep on her own in her bed, then think of ways to getting her closer to her bed while she's getting sleepy?