She entered wearing a blue denim jacket, but changed her clothing and left wearing a black hoodie, black joggers and white trainers, and was carrying a light coloured shoulder bag with a pattern.
She was seen to head west and turn down Preston Street.
Police are growing increasingly concerned for Jemma, who is not believed to be in possession of her mobile phone.
Please keep an eye out for her and dial 999 if you see her.
