How to respond to "you've changed"?

I have been increasing SMV, adding value to my life and becoming the best person I can be. I stopped taking shit from people, especially women. Thanks TRP. Before this I was such a beta loser. Lately I've been getting the "you've changed" from people. Especially some plates or former FWB that have been orbiting me for whatever reason. When I hear the you've changed I usually just come up with some smug remark on the spot or generally don't give a shit. One girl I used to fuck came over and cooked me dinner. I wasn't going to say no to a free feed and less work for me to do but we stopped sleeping together when she ended things between us. (Probably because I was still too much of a beta then). The end of the night she says to me in a playful way "you've changed, I'm going to head home now and leave you here with your sassy attitude". I just say, "oh is that right? Well don't let the door slap your ass on the way out". Her jaw fucking dropped to the floor but you could tell she was smiling behind it AND THEN she wanted to stay for longer. I laughed about it and said nah not tonight because I didn't have time for her and I was 100% sure we weren't going to fuck because she probably still sees me in a beta light.

I don't get it to be honest. Why do chicks say the "you've changed" line and pretend it's a bad thing but their body language speaks a different tune? To those of you out there that have heard these words before, what is the best response?

EDIT: To anyone who says I'm an idiot for not letting her stay for longer or I could have fucked her. I honestly say no, I don't think it would have happened. My gut was telling me that night she would waste my time. Besides, I have more self respect for myself than I ever have before and the fact she pulled back from the FWB thing with me and without going into detail how she did it as well (majorly giving me mixed signals) was disrespectful to me. If she wants back in my bed she's going to have to try harder than this.