The 14-year-old, from Harrow in north-west London, viewed an extensive volume of material, including some linked to anxiety, depression, self-harm and suicide, before ending her life in November 2017.
Her inquest will examine how algorithms used by social media firms to keep users engaged may have contributed to her death.
At the latest pre-inquest review in Barnet on Friday, the court heard submissions on behalf of social media giants Meta, the parent company of Facebook and Instagram, and Pinterest.
Molly was an active user of both platforms prior to her death.
It was requested that Elizabeth Lagone, head of health and well-being policy at Meta, and Jud Hoffman, Pinterest’s head of community operations, be permitted to give evidence remotely.
Oliver Sanders QC, representing Molly’s family, alleged this would be “disrespectful” to the family and the court, a claim refuted by Meta and Pinterest’s representatives.
He said in-person attendance is “gold standard”, arguing it aids communication and makes it easier for people to look at evidence, calling remote evidence a “compromise” and “suboptimal”.
Caoilfhionn Gallagher QC, for Meta, said this would require “significant travel” at short notice for Ms Lagone, who lives on the east coast of the United States, with “associated fatigue and risk of illness” from Covid-19.
She said her evidence would “not in any way be diminished by appearing via screen rather than in person”.
She said: “Our submission is that Ms Lagone should be permitted to attend the inquest by video link and that she give her evidence by video link in accordance with Rule 17 (of The Coroners Rules 2013).”
Andrew O’Connor QC, for Pinterest, agreed, citing Mr Hoffman’s “professional and personal commitments”, including a concern about catching Covid-19 and transmitting it to his elderly parents.
He said: “The fact is that the risk of Covid has not disappeared, in particular in the US, and international travel is a risk.
“As with Ms Lagone, he has now been preparing for this inquest for some time on the assumption that he will be giving evidence remotely.”
Mr Sanders argued: “There is no positive reason for hearing witnesses remotely and given that there is no positive reason Rule 17 is clear they must be here in person.”
He said the family do not want to “attack or blame” either Mr Hoffman or Ms Lagone.
“The family has questions for them,” he added.
“It wants to hear their answers and it wants to hear that face-to-face in the same room.”
The coroner sided with Mr Sanders, ordering them to give evidence in person.
He added: “I am not satisfied that the inquest would proceed more expediently by witnesses giving evidence remotely.”
Mr Sanders also asked Meta to divulge the redacted handles of Instagram accounts recommended to Molly, suggesting its algorithm may have been “promoting” “distressing” content to her.
But Ms Gallagher said they cannot disclose the account names under UK and US laws.
She cited GDPR and said the name of an account is personal data which could lead to the identification of “potentially vulnerable” Instagram users.
The inquest was postponed in March after thousands of pages of new evidence about her internet history were submitted by Meta.
The court was last year told how, on Twitter, Molly tweeted or retweeted 460 times, liked 4,100 tweets, was following 116 accounts and had 42 followers.
Molly was a much more active user of Pinterest, with more than 15,000 engagements, including 3,000 saves, in the last six months of her life, but she did not have a Facebook profile.
However, in the last six months of her life, she was engaging with Instagram posts around 130 times a day on average.
This included 3,500 shares during that time frame, as well as 11,000 likes and 5,000 saves.
The inquest is due to open on September 19.