She did not "dump" him; they made an agonizing decision after seven years together, and very much remained friends until his death. She was deeply in love and sympathetic to him; but did it occur to you that she may have wanted to have children and a settled life for them?
He wanted to explore his bisexual impulses, and at the time, the LGBT scene was if possible even more wildly promiscuous than today, since AIDS awareness would not come until later. Many married gays of the era tried to keep it "on the downlow" and also stay with the wife and children they loved. Given his fame, that was not going to be an option. She showed him understanding and let him go without rancor. He continued to talk to her by phone almost daily.
Growing up and initially denying his sexuality, he fell in with an artistically irreplaceable set of heterosexual bandmates who all had girlfriends or wives. If he revealed himself, would it break up the band or the friendship? He was also dealing the expectations of a more conservative society at the time, his Zoroastrian religious upbringing (which was honored at his funeral) and his respect for his parents (“Mama, I just killed a man...didn't mean to make you cry" referred to his own inner struggle, in my humble opinion).
Freddy with his mom (below), who outlived him by 25 years, dying in 2016 at age 94:
His mother was quoted as saying:
“Freddie kept a strict division between his work and his home all his life. If I ever asked, he would say, ‘Mum, that is business, and this is family.’ He was kind and very respectful both to myself and his father.”
That does not make her his common law wife.
She didn't name herself that; he did, in an interview with his biographer Lesley-Ann Jones published in 2012. Both had entered the relationship neither having come to the full realization that he would eventually identify as gay; it took him seven years before he eventually confronted the issue with Mary. There have been several other long biographies published over the years that detail their relationship, which took place in the rebellious 60s/70s when even hetero hipsters were questioning whether marriage was necessary.
For whatever reason though he declared that he would always love her. A couple of his songs are said to be about her.
The reason was that he loved her—as he, she, their families and his bandmates were aware at the time.
I always thought that she had already inherited the money.
The article, had you read it, explains that.