"It is particularly sad that she is not here to see the difference her donation has made to the lives of our trainees," centre manager Anne Ramsey told BBC News NI.
"Margaret seemed to have a real affinity with learning disability services. This is a wonderful legacy."
Ms Loughrey's donation, and further funding from the Kathleen Graham Trust, means "we can offer a much more exciting and varied range opportunities in house for our clients", Ms Ramsey said.
"It is brilliant to be in this position to enhance the range of opportunities and availability of our services in the north west."
It is hoped the 6,000 sq ft facility will become a centre of excellence in providing support to adults with a learning disability.
It includes an IT suite, training kitchen, hair and beauty salon, sensory room and music and dance studio.
Ms Loughrey, who had previously bought a car for New Horizons, pledged to fund the new centre during a meeting with management just prior to the outbreak of the Covid-19 pandemic.
"She talked about the wonderful work that we were doing," Ms Ramsey said.
"She could see the difference that it could make to individuals with a learning disability. We talked about our aspirations, about where we were operating from and the difference that her donation could make".
"But she said she did not want anyone to know, she was very particular about that."
A plaque in memory of Ms Loughrey has been put up on a wall at the centre.