"They do not have to come."
Translation:Zij hoeven niet te komen.
Meekomen = to come along, so I guess it depends on the context: if you are both leaving somewhere, then use "meekomen"; If you are waiting for her to come to your place, then just use "komen". As in English it is not absolutely necessary to include "along" in the translation of "meekomen", in previous exercises they didn't, and that must have confused you.But you should realize that, for the designers of the course, it is impossible to include all the possible translations. So they do not, and should not, include this kind of non-obvious translation from the beginning, but wait for the feedbacks instead. My point is, you should suggest the translation but not request it (and I am not saying you did, it is a general observation).
P.S: I am a native speaker neither of English nor Dutch, but of Portuguese.And I do not even speak Dutch yet.^^
Depending on the context in which it's said, yes, that is correct. Example: Your best friend tells you she invited certain friends to her party to which you are also invited, however, you don't like those particular friends and wished she hadn't invited them. Your response in Dutch could be: Ze hoeven niet te komen. Obviously, you mean that you really don't want them at the party. Your friend's response could also be: Ze hoeven niet te komen. By that she would mean "I invited them but if they don't come, that's alright with me."