My ds ALWAYS woke up after 45 minutes at your dd's age. Nothing I did changed it. I increased awake time, didn't work. Decreased awake time, didn't work either. I would pat/shhh, didn't work. Pu/pd made him FURIOUS! Ethan was just like Lucy - he'd wake up happy after 45 minutes. So, finally, one day, I just let him babble in his crib. And after about 30 minutes, he fell back asleep for another 45 minutes. Then I got him up for lunch. So, that became our routine for the next few months! He never really cried or fussed, he just rolled and crawled around his crib and talked to himself.
So, as long as she's not out and out screaming for you, I'd try to let her babble to herself, and see if she goes back to sleep!
That's just what worked for us. Good luck!