>>88270001PP's had a rough life. Yeah she can be obnoxious sometimes, but she can also be nice to Chuck, and he's actually pretty fucking shitty to her a lot of the time.
Peppermint Patty's one of a handful of characters in the strip who has any kind of respect for Charlie Brown, the others being Franklin, Linus, and I guess Marcie and Snoopy. She really likes him and just doesn't seem to see the faults in him that everyone else does. She looks up to Charlie Brown. Hell, even though her baseball team clobbers his, she doesn't seem to realize this and treats him and his team with respect.
Lucy LIKES Charlie Brown, but she doesn't respect him. She looks down on him just like everyone else, the only difference is she likes spending time with him, because she's a mean person and likes hanging out with people she can walk all over and talk down to, who won't resist much. And she really thinks she's doing what's best for him.
Lucy likes Charlie Brown BECAUSE he's a loser, and likes taking advantage of him. Peppermint Patty likes Charlie Brown, not even despite being a loser, she just genuinely doesn't see him as a loser, she just likes and respects him as a person.