Bobbi Kristina Brown is ''very proud'' of Whitney Houston's final work.

The 19-year-old Offspring of the late superstar and Bobby Brown is thrilled by new movie 'Sparkle', which the 'I Will Always Love You' singer worked on shortly before she died in February this year, and penned an open letter to her mother to praise her performance in the film.

Bobbi Kristina - who attended the Los Angeles premiere of the movie with 'adopted brother' and boyfriend Nick Gordon last night (16.08.12) - wrote in Ebony magazine: ''Mom, I know that making the movie 'Sparkle' meant everything to you.

''You always told me and Nicholas and the family, 'This is for you, this is for us, this is for the family. This is for you Bobbi Kris.' You told me that all the time.

''I'm so proud that you were able to finish making 'Sparkle' before things happened. You did it for us. Mom, you had such a great time making the movie. You glowed just glowed.

''My mother being so happy was an absolutely Beautiful Thing for me to watch. I'm very proud of you.''

Meanwhile, Whitney's sister-in-law Pat Houston - addressed the assembled crowd - including the movie's stars Jordin Sparks, Derek Luke, Mike Epps, Cee Lo Green, Carmen Ejogo and Tika Sumpter - ahead of the premiere screening at Grauman's Chinese Theatre and said she knew the late star would be ''celebrating'' the occasion.

Pat - who was accompanied by Whitney's mother Cissy Houston - said: ''I can assure you that Whitney is here celebrating right now. She would have been so humbled [knowing her family was in the audience.]

''To my mother-in-law, you did good. She did it.''

Whitney's on/off boyfriend Ray J was also at the premiere and said he was ''touched'' and ''emotional'' to celebrate the film.

He added: ''I can't even start with one thing [I wish people would remember about her]. It's just so much.''