How'd She Get In?

There was a lot of "Yeeollll!!! " and running this morning!
I came downstairs, and Walter and Pazzy were growling. A cat who I haven't seen ran off and she was gone.
I don't know how she got in through the cat fence, and she obviously came in through the cat flap, to be found by two boy cats that is very protective over their house.

I went to clean the litter box and there she was!!!!


She was scared but she did not resist when I gently picked her up. I tried to get her to the front door and then Paz spotted her and chased her upstairs.
She went into the upstairs room and crouched in the corner. I told Zumzum there was a Pazy upstairs, and she came to see, and said "Awwwww Kawaiiiiiii!"
I opened the window and she jumped off outside.

I thought that was the last time I saw her,
and then next day, at night, there was growling and running in the backyard.
I went to look and she jumped in our backyard !!!!!
Of course Paz and Walter got upset and chased her, and she tried to climb out the cat fence, and couldn't. I opened the gate and she was hanging off the fence, and jumped and ran outside.... Pazzy following her.....

 Why did she come back??? She must be someone's cat to have the nice fur, and know how to use the catflap.
But two days in a row???
My only theory is that she must be REALLY nosey, HIME class nosey.
Cute cat.