Is this the right way to read every line?
Too complicated. Just say:

for (std::string line; std::getline(_file, line); )
{
    // process "line"
}


The function std::getline, like most iostreams operations, returns a reference to the stream object itself, which can be evaluated in a boolean context to tell you whether it is still good, i.e. whether the extraction operation succeeded.

Also, the function shouldn't be called "parseLine", but "parseAllLines" or "parseStream".