What I have seen with my friends' kids is that some are short nappers and others are long nappers. For a baby, 45 minutes is about the length of their sleep cycle (it will lengthen as they get older - as adults our sleep cycles are ~3 hours long). I would look at her *total hours of sleep per day* and the 2 hour window between sleeping instead of trying to make each nap fit a certain length.
If you are breastfeeding, I would advise against going by the clock and scheduling feedings. That will hurt your milk supply long-term and also stop your DD from regulating her own eating (which is part of the purpose of breastfeeding and why it is healthy). A 9 week old nursing every 1.5-2 hours is 100% healthy and normal.
I think that cue feeding (watching your daughter's natural cues and desires to eat) are more important than following a book like Babywise or The Baby Whisperer. There is a reason babies want to nurse often and that is healthy and good for them IMO. I'd recommend this book to you: Breastfeeding Made Simple: Seven Natural Laws for Nursing Mothers by Nancy Mohrbacher It explains really well how the mother-infant bf'ing relationship is designed biologically and how to make it benefit both of you.
(FWIW, in just a few weeks your baby will fall into her own regular rgythm that you can follow instead of trying to make her follow an artificial one).
Mom of 4: Boy (10), Girl (7), Boy (4), Girl (2)