That seems normal enough to me. I wouldn’t give too much more information than a kid requests.
All I know is that two of my sons, who are both madly in love with Mudgirl, are going to be very jealous that she’s not suggesting marrying either of them! 
Just to clarify, her aunt is lesbian, not bi. But here’s the story (since you requested it):
hubby and I were driving down the highway, (then) youngest daughter, age approx 7 in the back seat. Daughter says to me:
“I think someday Aunt B might find a nice man to marry, so she can be happy like you and Dad”
Me: “She is happy. She won’t marry a man, because she has Aunt M, and she loves Aunt M like I love Dad”
Her: “But what about getting married?”
Me: “Well, the law says her and Aunt M can’t get married”
Her: “Well, that’s just dumb”
Me: "I agree, but that’s how it is right now. But she loves Aunt M just like I love your Dad. They have a house together, and they live together, and they love each other. See, Aunt B is what people call ‘gay’; most of the time, men are attracted to women, and women are attracted to men, but sometimes men are attracted to other men, and women are attracted to other women. That’s called being gay "
Her: “So, Aunt B is ‘gay’ and that means she loves Aunt M like most women love men?”
Me: “Uh, yeah, more or less”
A few minutes later, we pick up her older sister from friend’s house. Older sister was ~11 at the time and knew everything.
Younger sister to older sister: “Did you hear about Aunt B? She is SO gay!”
Rule 1 leads only to tears, estrangements, teenage pregnancies, and years of therapy.
Change 30 to 15, and change “violating rule 1” to “causing daughter even a whisper of emotional pain through infidelity or pressure to do anything she doesn’t wish to do, including changing favorite flavors of ice cream.”
Oh, lets not get her started on that! Soon she’ll be in favor of polygamy! 
FWIW, she counts your boys among her many ‘boyfriends’.
PS: Please don’t tell them she’s being actively ‘courted’ by a class-mate; they may be heart-broken!
Agreed. Currently, I am plotting the demise of my 17YO’s ex-bf. He was the very first bf she ever had, and as I had previously predicted, once she fell, she fell hard.
There were a number of ways he could have broken up with her that would have hurt for a while, and then she could have gotten on with life in general. But he was a dick and a coward about it, and now I want to kill him.
I think she’s at an age where she can just take in the facts and reach her own conclusions. I mean, most kids are able to do this. She will see you leading by example and she will analyze the facts and she will form her own ideas about the world. What you say probably has very little influence in comparison to what you do. There’s no need really to beat her over the head with the concept of homosexuality if you live a life free of prejudice.
Your story reminds me of the time I found out a very close family friend was gay. I’d known him since I was six and it finally clicked when I was 13.
My Aunt (who was his best friend) turned to me and said, ‘‘You just now figured this out?’’
‘‘Well, I just figured he was a really feminine guy.’’
‘‘Well, he is.’’
‘‘I mean, I know he can perform the entire choreographed routine to Madonna’s Blonde Ambition tour and can tell you the names and artistic strengths of her dancers, but I just really didn’t want to… jump to conclusions.’’
My Aunt and his sister never made it into any big deal, and he was basically like an uncle or older brother, so it never really occurred to me that this mattered. It was just a fact. The sky’s blue, that book’s red, Uncle Tommy is gay. Nobody made out like it was a big deal, therefore it wasn’t. One lesson I did learn from this (combined with my high school experiences of gay friends) is that if something looks like a duck and quacks like a duck, it’s probably a flaming homosexual. My husband makes fun of me because I think everyone’s gay. My defense is that at one point in my life, everyone was gay.
IF it’s done properly.
I think you did great,** norinew**.