Could a romanian speaker explain what până la means? Does it mean she will come at some point before six? That we don't know when she's coming but it definitely won't be after six? That she's available to come at any point before six? That she will come and stay until six?

She "comes until" six o'clock, does that mean that she will keep coming more than once, but after six she will suddenly stop coming back again? It really should say "She comes to six o'clock" or possibly "She comes at six o'clock" for better English, but there is the "or earlier" part that will go missing in that translation.