The shopping centre denies the claims.
Lucy Sheppard was 28 when she started experiencing dizzy spells, headaches and problems with her vision. When she collapsed at Langney Shopping Centre on April 27 last year, her friend Hazel Akehurst tried to dial 999 but found she had no mobile phone reception. She said she approached one shop worker who said it was against policy to call for an ambulance and described how a security guard also refused saying he thought she was suffering an epileptic fit.
Miss Sheppard started to come round and after failing to get any help, 27-year-old Miss Akehurst helped her friend into the car and drove her home to Southbourne Road.
Miss Sheppard continued to feel severely unwell and later that day went to accident and emergency.
She was admitted and doctors found she had a brain tumour the size of a snooker ball.
Miss Sheppard, who has a long-term partner and a son who was six at the time, said, "My whole world fell apart."
She later learned that the reason she was experiencing problems with her vision and extreme pain was due to bleeding in the brain.
Asked how she felt at not getting the help for her friend, Miss Akehurst said, "I'm very angry. I just don't understand why they couldn't have called an ambulance there and then."
Both believe Miss Sheppard could have died as a result of not getting the medical attention needed.
A week after being admitted to hospital Miss Sheppard was transferred to Hurstwood Park, which specialises in head injuries, where she was operated on.
Part of her hair was shaved and the tumour was removed. It was found to be benign and doctors told her the 'cavernous hemangioma' had been there since birth.
Ten months on and Miss Sheppard, who is now 29, is still recovering but doing well. At first she had problems with coordination, memory and spelling. She continues to improve and is now back at work as a healthcare assistant.
Mum-of-two Miss Akehurst is disappointed her friend has not received an apology.
Both women said they wanted to highlight the issue in the hope that shopping centre staff and the general public will be encouraged to respond to emergencies.
The security firm at the shopping centre said that an ambulance was offered and said the officer asked if Miss Sheppard was on any medication. The officers claims Miss Sheppard refused an ambulance.
Kevin Mclean, boss of security firm, Double Check Security said, "It is never a problem for us to call an ambulance."

• Lucy Sheppard and Hazel Akehurst will both be jumping out of a plane at 10,000 feet on March 20. They are doing a charity skydive to raise money for Brain Tumour UK. To sponsor them go to www.justgiving.com/lucyandhazelskydive