I think you just have to grin & bear it being thankful the 'long haul' is not SFO<->HKG. Otherwise, the blame goes back to the other passenger. Tell her there is a division of space; she is encroaching on yours and to move her baby carrier ( out into the aisle space?).

At the end of the day we all have to realize that non-private air travel is no different than riding Greyhound and it will not always be a pleasant experience.