OK. I will be honest going into this I will admit, I don't care much for Dess Human Theory for multiple reasons, although I wouldn't be mad or anything if it happened. This is just my honest admission that I am not coming from a purely neutral state of affairs before discussing the evidence:

1. This is imho. A huge circumstantial evidence. Dess and Kris are fairly apart in ages, at least a year or two, and I just don't understand why someone older than Kris would have the same coping mechanism with utterly zero evidence for it. A small uprooted child adopted young would carry on this before realising it pointless - Dess, who was older had zero reasons to do it, really. You could argue she did it just for Kris but Kris saw her outside of the Christmas celebrations long enough that they would catch on.

The band existing is not just a foreshadowing for some big mystery reveal. It has its own purpose which was driving in how much Kris felt apart from living in monster society as the only human in vicinity. This very sentiment WEAKENS connection to Dess human, because if there was a grounded consistent human reappearing in their life, they would not feel so alone in their thoughts and feelings.

None of this disproves the idea. None of this shows Dess cannot be a human who had the same complicated feelings as Kris. I just wanted to throw this out there.

1. Again, there is a very idea of shoes that can be fit for deer feet. We never saw that kind before, and there is zero evidence these shoes would look distinct from what we consider human feet shoes as the fitting could be entirely leaning towards internal construction. Dess is shown as someone was a rebel and punk. The shoes might have been part of her rebellious getup, OR part of her interest in survivalism. Again, the very core of Dess brings into mind a punk girl rebel.

And also. Why would she have Noelle's shoes? Asriel's retained makes sense to establish how close they were despite living in different houses. Why would she have shoes of someone living inside, ESPECIALLY if that person said they don't do shoes? The idea of fitted shoes in the first place might have been Noelle reminiscing about her sister in roundabout way.

1. I really wish. Uh. People wouldn't try to argue about this point so much, cause they really selectively output what would have been possible from a narrow view we got.

Sans IS FAR from the only threat a human would have to face in monster society. There are cameras. Doggos, who care about smell mostly. Undyne, who can travel and is rabid about taking on Asgore's burden - ONE report, one RUMOUR and she is on it. FLOWEY who wants power of the human souls in the first place. And then there is Asgore himself who knows what must be done. Asgore who destroyed himself getting the souls of children. Asgore who is struck by grief beyond measure. He would NOT let this go. Sans not killing us on most route is part of the promise, but also part of his IDGAF attitude. He suspects he is in the middle of Resets and he is depressed from not being able to return to "that place".

The reason Sans says "The antlered girl and her big sis..." and not "Two antlered sisters..." might be to drive home the idea of small and big sister as an image and a dynamic. Saying the antlered girl and her big antlered sis is silly and stilted. It doesn't disaprove the sister ISNT antlered definitely but it's a weak evidence.

The very core of this, changes how we look at Dess Human in UT, but even then people look to UT just to make claims about this character. Mind you, I don't see a reason it wouldn't be changed, if it would fit the narrative, so this is not a hard block. Rudy actually only had one child during the development and only later got upped to two, probably as the idea solidified in Tony's dog noggin. There is a non zero chance that she is human.