Why is this friend of mine indirectly telling me that I'm ugly?

Hi I'm new to Reddit, I don't know much about the format I hope this one don't get deleted.

Am I really ugly? Were the compliments I received from people just fake, while hers were true? I don't know which one to believe. I try to convince myself that people just have different preferences and that there will always be a few people who won't like my face. But... it really stings hearing it from a friend I've been trying to help build her confidence (let me call her Dianna).

I always hear this from her. She complains that she looks way too young for her age and wishes to look mature like me (we're both 19). At first, I thought she was being nice, but as days passed, I encountered another comment from her saying that I kind of look like I have kids and that I look 24 years old. And we all know what that implies.... I honestly don't know how to react because I don't want to view her as insensitive.

Another thing that finally made it clear to me was when she commented about my suitor. Here is the sequence of events: since I was trying to help her improve and build her confidence and communication skills, I introduced her to one of my friends (let's call her Anne). This friend of mine is really pretty! I know Dianna sees it too because she kept staring really hard at her face. After hanging out with Anne, she went home, leaving me alone with Dianna. While we were walking, she asked me if my suitor used to have a crush on Anne or had any feelings for her before me. I awkwardly said, 'No...?' then she replied, 'Are you really sure?' 

At first, I didn't know why it felt awkward, but isn't it weird to ask your friend something like that about her suitor? What is she trying to imply? Is she saying it's a stretch that my suitor didn't like or notice someone like Anne, or questioning why he would pick me instead of her? Why else would she ask that and even persist that I might not be sure? I was really hurt. Am I really that ugly that having pretty friends and a suitor makes it unbelievable that I was chosen despite having a much prettier girl around me? I was confused. I think I'm just overthinking so I need your advice on how to view this situation.

Should I talk to her about this, how do I do that? Do I stop interacting with her and completely disregard our 6 years of friendship?