Yup, this. This is the mantra that must be repeated when you have multiples. "I can do it because I have to." She will quickly get used to the crying (because she has to). And definitely refer her here or suggest a multiples support group. I didn't have any friends with twins when mine were born and honestly a lot of my single-child-at-a-time friends would try to give "helpful" advice that ended up being hurtful because they just don't apply in the same way with twins. I often ended up feeling inadequate, as if I should be able to not let a baby cry like my friends with singletons were able to do. And then even resentful for the "easy" life that they had, being able to love and focus on one baby at a time. The best thing my friends could say to me at that time (and even now) was/is something along the lines of "I don't know how you do it but they look GREAT. You amaze me." and "I know it can't be easy but you make it look easy." Those were always big pick-me-ups
My favorite from a friend's mom (a retired pediatrician): "Wow, they are FAT. Great job!" Let her vent and just acknowledge how she is feeling. It's OK to say you don't understand what she's going through but you believe her when she says how rotten it is
eta: another thing that helped was to validate what I was feeling: "that has to be so incredibly hard, I can't even imagine", say things about how well the babies looked "I've never seen such beautiful skin, you must be taking really good care of them!", comment on holding or feeding, etc two babies "I would totally drop one if I had to pick up two at a time!" and lastly...to BRING A DINNER. I am still grateful for those who brought by meals. They were SUCH a huge help!!!
And ITA about surviving twins being a huge accomplishment. I really wish I could put that on my resume. Something very interesting - we had to take Strengths Finders tests at work. I took one before I got pregnant. I quit my job after having the twins and 1.5 years later returned to the same job. I had to take another Strengths Finders test and it is VERY interesting that one of my top 5 strengths the second time around was "Adaptability". "Adaptability" wasn't even in my top five the first time. I think it says a lot, because most everyone who takes the test more than once reports similar outcomes. Multiples force you to become a whiz at adapting, and adapt she will!!