Yes, it can be a bit of shock and possibly a personal disappointment when your child comes out. Maybe it was for me when the first one came out - but less so with the second and third.
It may be a phase, it may not be. It's all uncharted territory for a 15 year old - even if they've known about themselves for a while.
It's good, and right, that you've had talks about sex. Consent issues still apply.
We've experienced some shitty attitudes (second hand) from parents of gay children who are friends of ours. Indeed my DW's cousin is/has behaved appallingly towards and around the matter of his son coming out.
Some can't cope, some see a ruined life ahead, some take time, some think of themselves - be it their reputations amongst friends, no grandchildren, family name dying out etc.
Looking back..... one of my moments was taking my daughter back to Uni one Sunday afternoon. I didn't really want to drop her off in the middle of town by herself so took her to meet her friends in a park. A dozen gay girls sitting round chatting. I was introduced - this is my Dad. I stayed for a while and came home thinking - this is fine, she's happy, they're decent.
And it's been that way for the past 20 years. Married, divorced - like many straight couples. But happy no, settled and secure.
None of my 3 are married but I've got 3 great sons/daughter in common-law.
Maybe/hopefully your husband will come round, accept it, maybe even embrace it. But you need to stand firm and support her - if he can't then he and you need to decide what's next.
We can't live through our children - we launch them into the world, we love them, equip them with lifeskills, decency, honesty but they are what they are.
And don't listen to any crap about it being a life choice.
All the best.