Yes, I agree with anna that LO is probably just a bit OT -- wake ups in the few hours just after bed are usually from not being OT through the day, but from being OT in that spell right before bed. I wouldn't feel bad about it, if she's sleeping well through the day and generally happy then you've not caused any problems, but I would try to deal with it now rather than waiting for probs!
6 months is usually when signs of dropping the catnap appear but it can take a couple of months for it to happen. If she is napping 1.5 hours, ending at 3pm, then I would try for a short nap at 5ish, which you MAY need to AP to get in -- ie/ walk, time in her swing, a bjorn, car ride, etc. If so, don't worry, that's totally normal! Let her have 30 minutes, and then she shoudl be ready for bed at 7/730ish and sleep a bit more soundly.