Vomiting episodes with Topamax Lamictal

Hi, I am new to this site and I have enjoyed reading through the various posts becuase it makes me feel connected to others who understand about epilepsy. My daughter is 14 and was diagnosed with absence seizures at age 9 and JME at age 13. She was on Lamictal for several years with good control, but once puberty hit, she had breakthrough grand mal seizures. The Lamictal was increased to 200mg 2x daily with negative side effects such as dizziness, moodiness and insomnia and she was still having breakthough grand mal seizures--even worse than before. Her doctor added Topamx at 25 mg 2x a day a few months ago with the intention of decreasing the Lamictal and increasing the Topamax. She is currently at 100mg of Topamax 2x a day and 100mg of Lamital 2x a day. Since starting on Topamax, she has had good control of seizures with minor effects such as some short term memory loss and word confusion. This is acceptable to her because she no longer feels spacy anymore, especially in the A.M. The primary concern I have is that as soon as she started on the small dose of Topamax and mixed these two medications mixed in her system, she has had bouts of severe vomiting at least once, sometimes twice a week. It usually happens in the middle of the night and the vomit is brownish in color--like bile. Both of her neurologists say this is not an effect of the medication mix, but so far, all of the tests that have been done on her internal system have been negative. The vomiting started the day she began adding Topamax with Lamictal and it always looks and smells the same. Sorry to be gross, but this one has us stumped. Our hope is to eventually wean her off Lamictal for good because seizure control on Topamax has been excellent while Lamictal just quit working effectively. She has had no other side effects like the weight loss, tingling or bad tastes in her mouth. Anyone ever experience issues with vomiting when combining or changing meds--especially these two? Any input would be greatly appreciated. Thanks!