So the difference between "taken" and "forgiven" is just that the later takes the dative form?
Yes, exactly. Another hint: 'sie ist vergeben' = she's taken. The present tense is reserved for only this meaning. You can't say she has passively been forgiven in a present tense. It's either 'I forgive you' - Ich vergebe dir, or 'she has been forgiven' - ihr wurde vergeben or ihr ist vergeben worden, or 'she will be forgiven' - Ihr wird vergeben (werden).
There's only one point I didn't understand.....if we use the passive form "she is forgiven", is it necessary to put "sie" in dative? I mean,if we want to say, for example, "I am vorgiven" shouldn't we say "ich wird vergeben", or we must say "mir wird vergeben"????
OK, and one last question, if I may .... it's that way with all the verbs (that in passive the subject(which was the object in the active) is put in required case), or it's like that only with this verb??? I may look a little bit dummy with these questions but I really want to know (cause in other anguages that I know it isn't this way).
Does this answer your question? http://german.about.com/library/weekly/aa012901a.htm If not, please ask again.
Let me tell you how I understand this case (you tell me if I'm wrong). If in a sentence which is in the active voice we have a subject (which is in nominative) and an object(which is in accusative), then in the passive voice the object turns into subject and is put in nominative. But then in this case ("ihr wird vergeben bei mir" : if we put the sentence in present tense and add also the agent,) the active voice would be smth like this "ich vergebe ES ihr", and we see that the direct object here is ES (which can be omitted) and ihr is the indirect object. So when we put this sentence in passive, we get "Es wird ihr vergeben bei mir". And when we throw away ES and the agent "bei mir" we get "ihr wird vergeben". That is my only explanation why in this sentence the object doesn't turn into nominative but remains in dative. Please note that it's just how I understood, and I'm asking you to tell me if I just said somethng incorrect.
Actually in English it's more correct to say 'She is spoken for' - meaning she's in a relationship. You'd say a seat in a restaurant was 'taken' but a person isn't a chair!
Agreed, saying a woman is taken could give the wrong impression! I took a chance and tried "spoken for" as my answer and Duo accepted as correct.
You can come up with a context in English where this would be ok. "For the next exercise, you need to choose a partner. "OK, Suzie will be my partner." "No, she is taken."