A lof of times the vomiting comes from a gag reflex from the crying...
I know my DD did this quite often when she cried for whatever reason and the Dr. told us this would get better as she grew, and it did, but she still has a sensitive gag reflex. I taught preschool and I was aware this was true for some other children as well.
From the show, it's hard to tell if she is vomiting from crying hard or ill from the stomach because she is so upset.
Just something to think about...
It will be interesting to see that when they do go to preschool if they will be all kept together or partly separated....
that will be interesting. there seems to be so much of a differing opinion on this issue. some feel it's essential to keep multiples together-some feel it's essential to separate and facilitate separate identities.
i don't know if there was 'something in the water'

or what, but i happened to attend school (elementary-local college) with multiple sets of multiples (not six or more, twins and triplets), and i found it facinating to hear them talk, as young adults, of how their parents chose to raise them (academicly), and what decisions they made-and how the kids felt it impacted them.
one set was strictly raised together (girls)-their parent's insisted they be in the same classroom k-12 (dad had prominance in the school district so it happened). as adults they complained that when things came up re. class plays and teams they never felt like they were independantly judged-but based on 'both', so they wondered those times when neither was selected/cast-was it because they were both lacking or that the adult did'nt want to select one but not the other (and they wondered if when they were cast, selected if it was for the uniqueness such to garner a crowd). one family had the kids separated from day one-they said in the younger grades they longed for their sibs, but it forced them to establish friendships based on themselves. as adults they ended up in the same activities, but while they had tons of mutual friends-they also had some very strong bonds individualy. one group (twins) were kept together through elementary/jr. high but when they hit high school their parents decided since they had identical interests they would send them to 2 different schools. both loved the fact that they were not competing against their sib for roles/places on sports teams-and realy appreciated that their parents gave them an opportunity to experience a setting where they were themselves-alone.
i get confused by what the gosselins say vs. what they do on their show. kate said in a recent episode that they purposely choose and appreciate surrounding themselves with people who can love and appreciate the kids for 'who they are not what they are', yet, when you watch the show there seems to be such an emphasis on exactly WHAT they are. kate seems to be obsessive about their clothing when they are in the public-all of the boys matching, all of the girls matching (and the twins in separate but matching apparal), their issues with needing private access to activities because of the attention they garner (yet they have their show's camera crew there to film every moment).
i felt saddened on the 'memorial day' episode when the twins fled from the picnic tables after kate decided to use these vs. the picnic blanket for the little ones to eat (the twins originaly chose the tables over the blankets specifical BECAUSE the little ones were there); kate excused it away as something to do with-there are lots of people here. they are begining to notice us, and the twins don't want the attention. yet a heartbeat before she said they were habitualy opting to sit separatly because they were growing up (um...my dd is older and feels much more mature than her younger db-does'nt mean i let her sit alone or with a friend dining with us at a separate table at a restaurant

). if the twins are starting to separate themselves due to personal discomfort, in situations where the very limited public localy reccognizes them-how the 'h' must they feel when every potty, bathing, personal moment of their lives are being recorded for international airing??? and lord help me, when kate said that maddie is now using the tv cameras as her personal conscious such that when she's being filmed hurting a sibling she realizes she has to hug following it because she does'nt like the way she sees herself-i got sick to my stomach
i have to wonder what the deal is.