Issue creating a bikini bottom without pixelated edges GIMP

So I have been trying to add a new imagine to use as a pattern on top of  an existing bikini bottom in the sims using gimp. I have been doing the following 

Paste As --> New layer   ----> clicking on the first layer (bikini bottoms)--> Fuzzy Select (clicking on the background)   ----   then clicking on the new layer (with the new texture) --> command x

Every time I do this I get the most pixelated edges and I cannot figure out how to fix it! I have tried doing this multiple bikini bottoms and this has been the case for them all. I have done this many times before with different clothing items and this has never happened. How can I fix this?


this is what it looks like