Laura Plummer's sister Rachel said their mother had been denied a chance to "say goodbye" to her daughter because she had been taken early to a prison in Qena.
"No prisons are nice but I think Qena's the bad one, which is terrifying for us because we fear for her so much," she said, a day after her sister's three-year sentence.
"She's just not cut-out to be in a prison, even in a UK prison never mind a prison abroad."
Rachel Plummer said mother Roberta Synclair had been in the Egyptian court for the shock judgment and saw her sobbing daughter being taken away in a "cage".
"Mum was told that she was going to stay in the Safaga holding cell, the police holding cell, for the rest of the week so she can visit her, take her things that she needs, food and stuff.
"So she travelled in a taxi today all the way to Safaga, which is an hour away from where she is, to be told that Laura had gone. She went to Qena (on Tuesday).
"Obviously that's even more devastating for my mum because she's not got to say goodbye to Laura.
"She's not been able to give her her food and her things."
Laura, a 33-year-old shop worker from Hull, was sentenced by judges some three months after 290 tramadol tablets were found in her suitcase.
She claims she was taking the tablets for her Egyptian partner Omar Caboo, who suffers from severe back pain and had no idea what she was doing was wrong, given the tablets are legal in the UK.
"All the evidence was presented to show that this was a massive mistake and Laura's intentions were as she said, just to treat Omar's back pain," Rachel said.
"I think they know she's not a drug dealer."
Rachel said she was unsure of a potential appeal.
Local MP Karl Turner said on Tuesday he had spoken to her defence lawyer in Egypt who said Ms Plummer had 60 days to launch an appeal.