Jebina Yasmin Islam said “there aren’t enough words to explain how much” her sister’s murder still “hurts inside”.
Ms Nessa, 28, was attacked on what should have been a five-minute journey as she walked from her home in Kidbrooke, southeast London, through Cator Park on her way to meet a friend at a pub on 17 September.
Her body was discovered nearly 24 hours later covered with leaves near OneSpace community centre in the park.
Speaking to ITV News London, Ms Islam said:“Boris [Johnson] needs to do something. Sadiq Khan needs to implement something for us to feel safe to walk the streets alone.”
She continued: “We shouldn’t be going home extra early just because we don’t feel safe.
“We are independent, we live in a country where we can walk alone but we can’t because of what’s happening, what happened to my sister, what has happened in the past.
“We need to make sure that this does not happen again and Boris, Sadiq Khan, they need to step up.”
Ms Nessa’s family organised a celebration at the weekend to mark what would have been the primary school teacher’s 29th birthday.
Garage worker Koci Selamaj, from Eastbourne, appeared in court last month via videolink from HMP Wormwood Scrubs, charged with her murder. The 36-year-old is next due to appear in court on 16 December for a plea hearing.
“You don’t feel like this would happen to you,” Ms Islam told the news broadcaster, as she explained the aftermath of her sister’s death.
“The world is carrying on. Who would have thought it was five weeks on that she’s passed away? It feels like we got the news yesterday.”
Speaking about her other siblings, she added: “We’re four sisters, we’re not three. We’ll always be four sisters even though she’s not here.”
Ms Nessa’s murder came just six months after 33-year-old Sarah Everard was abducted and killed by a serving police officer in London, sparking national outrage about the safety of women in the capital and beyond.
The prime minister, home secretary Priti Patel and justice secretary Dominic Raab all used their Tory conference speeches earlier this month to pledge their commitment to making the country a safer place for women.
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