I liked the one-shot but Amy was atrociously out of character, Amy has always been shown to be a caring and supportive friend, not a lunatic that tries to whack the sadness out of someone because it's annoying her. Cosmo was her friend too so she would understand how upset Tails is, she also knows what it's like to not be able to be with the person you're in love with. Amy has been shown to get jealous from time to time but everyone does! A good example of this is the Archie Sonic comics, she was definitely jealous of both Fiona and Sally during their time dating Sonic and she remained friends with them until Fiona turned traitor and left the Freedom Fighters, she stayed good friends with Sally despite her feelings for Sonic because she saw how happy they were together. She wouldn't attack her grieving friend because she's jealous of his love returning his feelings for her, she would try to comfort him to the best of her ability