At 14 weeks, my baby was up after 45 minute naps and not very happy.
At 15 weeks, she took a two hour nap, so I knew she could do it, and she was much happier. After that first two hour nap, it occurred to me that she was waking at 45 minutes, but needed to soothe herself back to sleep for at least another hour. I listened with the monitor for the next week, and sure enough, she was waking at 45 minutes on the nose, but I think all of a sudden she was just mature enough to find her thumb and go back to sleep. She is definitely a happier baby. Also, since sleep begets sleep, she is even sleeping a little longer at night and during her last catnap of the day. Her total at 18 weeks is 17 1/2 to 18 hours a day (12 1/2 at night, 2 - 2 hour naps, 1 - 1 hour nap).
I think you should give her a little more time, but also, don't rush in the room when you hear her at 45 minutes. Give her a little time to put herself back. I think, and I have read, you know your baby had enough restorative sleep when they wake up smiling, not crying.
Hope that helps.