There is a biography of Victoria Melita called "A Fatal Passion" by Michael John Sullivan, published in 1997, that asserts that Ernest was homosexual or bisexual and that contributed to Ducky's desire for a divorce. When they married, they discovered they were "sexually incompatible" and Ernie discovered he "could not be an adequate husband to her" and "he was not attracted to her." That's on page 136 of the book and is apparently quoted from an biography of Ducky's sister Queen Marie of Roumania.
On page 182 of Sullivan's biography, there is a recounting of Ducky's apparent discovery of Ernest in bed with one of the stablehands when she returned unexpectedly to Darmstadt. Here is the direct quote from the book:
"Exactly what happened will never be known, but to judge by what Ducky told her niece years later, she saw Ernie in bed with one of the teenaged boys employed in the palace kitchen. So great was the shock that Ducky was physically ill for several days, unable to face her husband or anyone else in the palace.
"As she gradually regained her composure a deep sense of shame replaced her grief. For apparently almost everyone in the palace knew of the grand duke's proclivity. While Ducky had been away in Romania, he had been left alone to freely indulge it, and he had apparently carried on in the most indiscreet manner. 'No boy was safe,' Ducky bitterly told her niece, 'from the stable hands to the kitchen help. He slept quite openly with them all.' "
The above is a quote from Terrence Elsberry's Marie of Roumania, according to the footnotes by Sullivan.
Elsewhere in Sullivan's biography of Victoria Melita, he states that she kept silent about Ernest's homosexuality. About 30 years later, when her niece, Princess Ileana of Romania, found out that her fiance was gay, Ducky told her about what happened with Ernest, according to the book.
Obviously no one was to blame for the death of little Princess Elizabeth. Typhoid was unfortunately common in that era, and contaminated water a common hazard. I think that Ernest and the Tsarina Alexandra and other adults CAN be blamed for not notifying Elizabeth's mother that her daughter was ill in time for her to reach her bedside.
In Robert Massie's famous "Nicholas and Alexandra," he states that Alexandra ignored the advice of the doctor that she should notify Victoria Melita of Elizabeth's illness. Here's Sullivan's account of Elizabeth's death:
"But one morning Elizabeth woke early, complaining of a dry throat and severe pains in her chest. Within a short time she was 'in agony, panting feverishly for breath.' A doctor was immediately called, but he could do nothing for the suffering child. More specialists arrived. Elizabeth failed to respond to their treatments. Alarmed, 'the doctors warned the Tsarina that the child's mother should be called at once.' Alix ignored their advice until Elizabeth's condition deteriorated so rapidly that the doctors insisted.
"Ducky was having breakfast at the Rosenau when the message arrived announcing her daughter's illness. She immediately went upstairs and began packing her bags.
"But another telegram arrived an hour and a half later, describing Elizabeth's condition as 'grave.'
"Ducky became frantic. She stopped packing, quickly grabbed all she could carry, and ran to her carriage. But just as she was leaving for the train station, the postman came galloping up the road with a third telegram. It was cruelly brief.
'Ducky's little daughter had just died.' "
Here, Sullivan is quoting from John Van Der Kiste's biography"Victoria Melita."
From reading this biography, and Massie's account of the same incident, I think there was probably plenty of blame to go around in that marriage and for Elizabeth's sad life. Ernest "adored his daughter" and was apparently a good father who lavished attention and affection on her. He even spoiled her.
According to Sullivan, he built a small playhouse in a garden for Elizabeth and adults were allowed nowhere near it until the little girl was willing to come out. Tutors and nannies paced impatiently nearby because they weren't allowed to order her to come out and learn her lessons.
But, at the same time, it sounds as though Ernest was gay and was pressured by Queen Victoria into a marriage he really didn't want. He was attracted to his artist friends, the good-looking boys on his estate, and not to his wife. He was cursed by his time and his place and his family. It wasn't his fault. It also wasn't Victoria Melita's fault. She was 17 when she was pressured to marry Ernest, had never been told anything about sex, and was completely unprepared for a marriage of that sort. The marriage was intolerable for both of them. I fault Ernest for not trying to foster a better relationship between mother and daughter and for not notifying Victoria Melita when the girl was on her deathbed.