I think it makes COMPLETE SENSE!! Yes she was sad about it...but we have NO PROOF of his death...like a body or anything.....and at the time she may have thought to have killed him off....but she may come up with another plan.....I mean...she really was sad about it..and he must've been a favorite character of hers....?? maybe not though.....
ok the "veil" did not kill him! he was supposedly hit with a curse by bellatrex! i dont buy that one bit though! ok look at it this way if she was gonna kill him by the avada kedevra curse then she would have written and sirius was hit with a jet of GREEN light.... but she didn't she kindly left us hanging b/c she did not say what color at all hit him!! the only time she mentioned the colore was when that one spell hit sirius and then he replied with come now is that all u got?? then she said that was a red jet of light!! so there are no facts proving his death or anything of the sort. but as for ur question, Sirius did not die from the curtain and it wasn't a curtain it was a veil
i dont think aveda kedavara is the only spell that could kill s/o thatd be totally lame. like in hp3 when harry is beating the **** out of sirius and hes about to KILL him but then lupin came....harry didnt even know about avada kedavara yet so how was he supposed to kill him if thats the only killing curse?
and ladyblue eyes shes not telling us her future intentions for the future books....it was her intention for this book! she just didnt want everybody to be convinced that sirius was coming back or that he was alive and then be disappointed when he didnt return..i mean cmon it would be a totall pissoff if u thought he was coming back and then found out he wasnt...its like closure for the harry potter geeks/fans or whatever ya wanna call em! 🤓