Hi, at 5 months she should be able to cope with staying up for 2-2.5 hours, before needing a nap. It's great that you are following her cues, sounds as though you are doing a great job! If she is only sleeping for 45 mins at each nap, you could try to work on amalgamating them, so that she goes through 2 sleep cycles instead of one, ie: sleeps for 1.5 hours twice a day, and maybe plus a cat nap until she is ready to drop this one. She probably is tired, as you have been watching for her cues, so if your current routine suits you, I wouldn't worry about it too much.