Dear OP,
We've done Maui from DC two times, and we built in every kind of 'make it less stressful on the body.' (I wasn't pregnant but have some chronic illnesses that make traveling hard and that flare things 'weirdly'). Even with that (spending the night in Portland on the way out to avoid jet lag, most comfortable seats possible on best airline [Alaska, INHO[, etc.,. it was awful and took my body two days to recover, meaning I had to do multiple brief rests, longer sleep at night, etc.,.
I've also seen two recent news stories about pregnant women getting 'stuck' in Hawaii because the flight out caused complications and they had to deliver there. I am not trying to scare you, but rather am making sure you know that any concerns you have and the comments you're seeing here are very, very real in terms of caution.
Your friend will understand, and if she doesn't get it now, she will when she is in her 2nd or 3rd trimester of pregnancy.
And if you do cancel or SKYPE, remember, you're not making that choice because of yourself or your friend or even your toddler, you're making it for your new baby, who needs the downtime more than the havoc of long flights

.
Good luck!