There is no disease or disorder associated with PDA.. ._. PDA only means Public Display Affection which is hugging/kissing in public. It's pretty normal not to like it. ~Grimmy~
It really depends on what you mean by PDA. If she has a problem holding your hand then I'd understand your concern, but if she doesn't want you tongue kissing her and feeling her up in front of others then I could see why she has a problem with it.