The phrase "although she promised" is correct and usable in written English.
It can be used to introduce a contrast or contradiction between a promise made by someone and the outcome or situation that follows.
Example: "Although she promised to attend the meeting, she never showed up."
Alternatives: "despite her promise" or "even though she assured".
"No, this is different," Ms. Hilton said of the show — although, she promised, "anyone can apply".
But her transparent attempt to duck the question about social care budgets being cut in the last parliament allowed Corbyn to score a direct hit, and, although she promised that her government would be the first for decades to "get a grip" and address this properly, nothing the government has said (so far) makes this pledge particularly credible.
Although a native of Chicago, she promised her collection of modern art to the Met in 1980 and over the years donated important works to the Costume Institute and department of photographs as well.
Madonna worked her socks off on Evita and she delivered everything she promised in the letter although, true, there were times when we wanted to throttle her".
Although she has promised a cut in income tax, she also campaigned on a pledge to raise corporate tax.
The introverted scholar will also seek to reshape relations with Beijing although she has promised to uphold the uneasy status quo between democratic Taiwan and one-party China.
Although she had promised to live until 2001, her deteriorating condition made her followers suspect she would die before then, causing them some distress and denial.
"I am very committed to you... at this time," Adam says carefully, after Hannah says that although she always promised herself she wouldn't get married until she had a swimming pool in her living room, she kind of hoped they were headed in a committed direction.
Although Caridad promised Pina that she would eventually send for everyone, the others had little choice but to make do.
Although May promised the conference she was not making the story up, the judicial communications office, which represents senior judges, insisted the tale was not true and said it had told May's department as much.
Palmer's Machiavellian wife is now his former wife, although Fox promises she will make a dynamic return.
