I've been on Lamictal for three years. My understanding is that rashes from Johnson Stevens Syndrome will show up in the first three months after starting the drug, and it's pretty rare. If you notice "any" rashes during that timeframe, report them to the doctor immediately. I didn't get Johnson Stevens syndrome, but I had several rashes. They varied a lot, and were in different parts of my body. I wasn't completely rash free until this last October. I reported each new one to my doctors (PCP and Neuro) they both told me that they had nothing to do with the medication. As @santosha said, "Every person reacts differently." Side effects vary. My rashes were harmless though definitely from Lamictal. My point is that, your daughter may get rashes from the med, and it's important to report them, but it doesn't mean it's serious. Other than some brain fog, and what I call "brain glitches", I've handled the drug reasonably well, and it's been effective.
Side note: The "brain glitches" are hard to explain, and I don't know if anyone else gets them. Other than being a bit awkward when having a conversation, they don't worry me.