With going out, can you block out visual stimulation for her? I found this to work quite well with DD in the sling, I never got her to nap well in the pram!
I do still think you're going to need to push A times during the day, 4mo is the time when many of us find we suddenly need to push but don't quite believe it
Waking up earlier from naps and having NWs can often be a sign that they need more A time, also being harder to settle. You're right that 2h is on the upper end of average for her age but they're all different and you may well find that she needs longer. The regression will pass but her A times will still increase. Try increasing the first one to start with and see how she does, but you'll probably need to do something really calming just before as her body will still be expecting to sleep at the old A time so she'll be acting especially tired.
Btw I'm away for a couple of days and won't be on here, will check again Saturday night but not ignoring you in the meantime!