These are always the most difficult of times - and I find myself in an almost identical situation to you, but if I may, I would like to add my thoughts for you.
I am a believer in the fact that rabbits know and sense when their partner is poorly and much has been written and evidenced about the perception of animals over humans.
I know from the behaviour of my bridge bun Ben, that he most certainly grived over the loss of his wife bun Georgina. He was with her by her side when she slipped away 2 years back now.
Rabbits, like us, have emotions. They just don't vocalise it but I am certain that they are quite capable of holding a variety of emotions.
Should you have taken Susan with you with Dillon? In my view, as tough as it is, I would perhaps suggest not. What you are feeling, is the frustration of not being able to either change or turn back time. I would suggest that Susan should be given the chance to say her goodbyes. She will do it in th eway she feels she wishes to. But I feel it is right to give her that moment.
Her loss of appetite in my view could be an indication of her grief - a sense of not being able to understand why Dilly is not there. As a comparison. Lillian here has not shown any dip in eating and is more or less continuing to eat (and eat and eat).
I have the utmost respect and admiration for you with your updated information about going to see 'Rabbit de nero'. I am immensly proud of the fact that you feel in a position to move forward, despite dealing with the tragic loss of Dilly. I wish I had an ounce of the strength you had. And again, for each and every one of us, moving on is something we can only chose to do when we feel ready to.
Again, I feel that this is the right thing to do, in the circumstances that you wouldn''t want to find yourself in. And again, you have far greater strength than I do right now because I am still struggling to face each day and know that I must find a path to move forward, but I just cannot find that.
It is I feel, imprtant that our rabbits share their lives with a companion and whilst there are sometimes factors that lead buns to live fruitful and happy solo lives, they benefit immensly from the bond shared with another rabbit. Yes the bonding process has to begin again, but you worked tirelessly and so strongly to bond Dilly with Susan, that you have a very deep and genuine desire to persevere and get the positive outcome that you and Susan deserve.
I feel Susan should have the chance to share her life with another bunny. Dilly was a warm, gentle and unique rabbit, who gave love as well as received it. A new bun won't be another Dilly - as much as perhaps in your heart you would like him to be. This is the very question I ask myself from the moment I wake to the moment I sleep.
I hope you can at least draw some help from my views. I do genuinely share your pain right now and I am so pleased that you feel ready inside to move forward in such a positive way and I hope to read some exciting news in the coming days regarding the potential new bun.
Bless you and I hope it goes well.
Craig x
I think you said (I probably got muddled) she wasn’t eating so well before Dillon had gone? I would call the vet and see what they say, she might need some gut meds to get her guts moving again. Her teeth might need checking over to see if everything is ok with them too. 
