it may not be wrong but whilst she is in recovery, and for your belief that she is "relieved to be out of the relationship" i still think she will want/need a little time to complete the distancing process.
However much she might say she doesnt mind, when you ask her, she may vell i believe think less of you for not supporting her completely for this period and you may well find she moves away from you either for a while or for ever.
How strong is your friendship i wonder ?? and how important is it to you to be supportive of her , or do you not feel that supportive ??? especially as you think he came our of it worse....................... an interesting justification of your actions i wonder ???
As everyone says, there will be repercussions of you pursuit of your friends exs friendship and one of his mates........................it is dependent if it will all be worth it in the end !!
Good luck