The 20-year-old had previously been joined by Laurie Harries in the extended squad but her quest is over after suffering a shoulder injury.
A squad of 23 GB Sevens players continue to train full time in Guildford under Team GB Sevens Head Coach Simon Middleton and assistant Richie Pugh.
Ongoing Olympic preparations will be supported by Rugby Europe’s tournament in Kazan (11-12 June) and an invitational event in Tignes (14-16 July).
Middleton has been impressed with both Joyce and the recently departed Harries during his intensive training regime.
“Jas has got great pace, fantastic ability around the contact area and alongside Laurie is a pleasure to work with and both bring a lot to the squad in terms of character,” he said.
Joyce is pleased with her own progress since joining the programme.
“All the support we have had for conditioning, improving our fitness, our speed and defence has been amazing,” she said. “Before coming here defence was my weakness but now it has become a benefit for me.”
Pugh believes the squad are in a ‘good place’ but realise there is still plenty of work to do before reaching Rio.
“I definitely think this squad is capable of going for gold from what I have seen,” he said. “There are a lot of good teams capable of achieving that but we are definitely up there.”
