Neil Black, the British Athletics performance director, admitted the decision over the middle-distance runner had been "very, very tough".
Weightman said the setback would not affect her progress.
"If 11th in Rio is not seen as successful, it is difficult to know what is. The funding is helpful, but I'm very lucky that London Marathon provide support," she told British media.
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"This will not halt my career," she added.
It was not immediately clear why Weightman's funding in particular had been cut. Athletes receive funding based on a wide range of criteria and performance expectations.
Weightman finished 11th in the 2012 London Olympics 1,500 metres final. But it later became clear that six of the runners in front of her served bans for failing doping tests.
The anti-doping programme in Rio was also called into question after the World Anti-Doping Agency released a report last week saying there were "a number of serious failings" with it.
Weightman said she would not be surprised if she had finished behind drug cheats in Rio.
"Here and now in the moment people could be losing their funding. Who knows if anyone in that final in Rio was cheating? You want to know everyone is clean," she added.
"But it is the reality of the sport at the minute. After what happened in London, you just don't know."
(Reporting by Shravanth Vijayakumar in Bengaluru; Editing by Hugh Lawson)
