Every baby feeds differently, so I wouldn't stress too much about the exact numbers, but I do think it's worth mentioning to your PD at the next visit just to get a proper check, especially since the amounts vary quite a bit between home and outside. Honestly, when we were out my baby also drank less, and I later realised it was because she was distracted or the latch wasn't as comfortable in unfamiliar places. If your baby seems satisfied, is gaining weight well, and has enough wet diapers in a day, those are usually good signs. But because she is only 3 months, I would still bring it up with the PD to be sure, rather than guess on your own.