You don't see anything wrong with aggravating a god?... Why not shoot 8 or 10 times if she is a tough Asgardian? He has nothing to gain by not shooting, and nothing to gain by not calling out for Sif...IDidn't Sif say her voice casts a spells? Maybe he was under a spell the second she spoke. Plus, if Ward took Lorelei as being similar to Loki, shooting her and failing may have resulted in him getting stabbed like Coulson. I think he was using himself as bait, non-threatening, for Sif to finish her off. .