I Swear She's Trying to Kill Me

The weather here has gone from bad to worst over the past week. Between the torrential winds, rain, and even tornados we have not gotten much hunting time in. I have gotten in the habit of hunting her home but the game is scarce. We have gotten very few slips lately, but she has given it her all.
Monday, after a two hour drive home stopping at all the places I usually find birds, I gave up. I ended up going to Tom's house and decided to take her on a walk through the trees in his large yard. She did great for a bit and her response was on key. She then discovered a large vine-covered bush that housed a lot of sparrows. This was new to me, but cool! She had perched over the bush, so I tried to get them to flush. The little buggers held tight. I finally got one to flush and she proceeded to chase it across the street. Not a problem, his street is not busy at all. She landed on the ground next to the neighbor's fence and I started to walk across the street to collect her from the ground. As I get about halfway across the street, a cat comes out of nowhere and decides that it is dinner time. I start to run and the cat immediately bolts, thankfully. Scarlet had other ideas however. She immediately disappeared through a crack in the fence and proceeded to chase the cat on foot. This was no small cat either. Again I ran, scaled the fence, chased the cat off and picked her up. She was still puffed up and defensive, but I soon had her clam and eating. I gave her a good look over and she was perfectly fine. I, of course, was now in great pain from my acrobatic attempts. First the tree, now the fence...I am pretty sure she is out to get me.
The only other question I have: why will she chase huge cats, but not grackles? This is a strange one.....