I m not surprise you re in a muddle. But you want to know what happens when your daughter, a Catholic, ventures to Communion in a Protestant church. In my view, she has violated none. There is no exact teaching. That, of course, is open to debate, even among Catholic theologians.
Sacraments are moments of grace.
Nobody says that. The origin of Communion is, of course, the Last Supper, in which Jesus offered his body and blood for his disciples and for the whole world. One of them, after all, promptly went out and betrayed Jesus. There are many answers, none seeming to cover all bases. So what your daughter has done fits into a much larger discussion of the origin and purpose of the Eucharist, one that leaves theologians with various interpretations.