Congratulations - how exciting!! I have fraternal twin boys that will turn 16 in a couple of weeks. I was 30 years old when I had them and had no other children at the time. I am 5'4 and weighed 115 pounds when I got pregnant with them. I really had to focus on gaining weight early in my pregnancy since twins tend to be born early and the doctors wanted them to be as big as possible as soon as possible. Other than morning sickness for the first trimester and having to eat way more than I was used to in order to gain weight, my pregnancy was a breeze! Twins are considered full term at 38 weeks. Thankfully, I made it to 38 weeks and had to be induced. My boys were both born vaginally 14 minutes apart - one weighed 6 pounds and the other weighed 6 pounds 7 ounces. They were healthy and had high Apgar scores so were able to take them home from the hospital 27 hours after they were born.
The first few months were HARD. Even though many people offered, my husband and I wanted to do everything ourselves without any help, so it was just the two of us with our boys for the first 4 weeks and then it was just me and our boys until I went back to work when they were 12 weeks old. They didn’t sleep through the night until they were 6 months old and that was really rough! After they started sleeping through the night and my husband and I were able to sleep through the night again, things were SO much easier!
One of my boys did have torticollis and had to go to physical therapy and wear a helmet for 4 months when he was 6 months old. He was Baby A and the doctor said that his torticollis was a result of the position his head was in during the last couple weeks of my pregnancy.
Twins are so much fun! When my boys were babies, I just loved listening to them babble back and forth to each other, stare at each other, play with each other, cuddle with each other, etc. It has been amazing watching them grow up together. I absolutely adore their relationship and witnessing it makes me sad that their little sister doesn’t have a twin to go through life with!
I know it is easier said than done, but right now my advice to your daughter is to prioritize herself and take really good care of herself! I got pregnant with my boys on our third attempt at IVF so I made it my mission to take extra, extra, extra good care of myself and I think it definitely paid off! Good luck to your daughter! If you have any questions, please let me know. I am more than happy to help!
At least with the little one they already have, they have some help with diaper delivery! 
And having a toddler on hand for goofy entertainment purposes can be awesome too!
