Every bride has the same dilemma, if not a pregnant bridesmaid or people overseas, bridesmaids come in all shapes and sizes and It's always going to be hard to buy dresses for people that live some distance away.
I would recommend not to buy the expensive made to measure dresses, as this will be even harder to manage. Even though brides like to think that bridesmaid dresses will be worn after the event, the maids will very rarely do this, and so it's best to buy dresses that suit your theme, fit well, and do not go over budget!
I got married last July and bought my dresses from Marks and Spencer, months in advance. I had 4 adults maids (Size 8, 10, 14, 18) The dresses were full length duchess Satin which stretches, and I found fit every size as well as I had hoped, plus the dresses were long enough to be taken up for the shorter maids with ease. I later recommended the same dresses to a friend who got married in November, and she had a bridesmaid from italy and one who was pregnant so not too dissimilar to you.
I have looked and M&S online exclusive range and they still have the same dress, as well as new styles. Have a look at M&S wedding shop (www.marksandspencer.com)
Depending on what you choose, If you do select duchess satin dresses, they could be easily altered to fit the growing baby bump by removing the skirt lining at the waist or choosing a less fitted dress that is empire line to fit under the bust giving room for bump.
Your bridesmaid overseas - You could also ask your bridesmaid to send measurements and compare these with the dress once you have bought it, or post the dress overseas recorded post and if it doesn't fit the dress could be sent back and exchanged for a different size.
I hope this helps you