I grew up hearing and became HoH during my university years. I agree, do learn sign language as a family. Honestly, it makes tons of difference if you have to struggle communicating with your family, or if you can do it easily. Encourage her to find ways to compensate the hearing loss using vision instead. A lot of eye contact when communicating.
The good thing is that she is not the first one nor the only one to loose hearing. There are a lot people who handled deafness before. Many of them successfully with jobs they enjoy and families they love. Go and meet others in similar situation and find role models. Especially as a teenager it will be important for her to see that there are other people in her age that don’t hear as well. If there are no other Deaf kids around, I would even consider moving. Or at least make sure she goes to summer camps or school where she meets other Deaf children.
I assume people react very differently to her just because of the lack of hearing, so make sure she knows she is still the same person as before. It’s just the hearing that changes, not the rest of her. I mean if she loved strawberries and was good at math in school, nothing of that actually changes, right? It is important not to overestimate what deafness means. She needs a lot of creativity and self esteem to find out how to handle things without hearing. Hearing people around her won’t really know what to do, so she will most often be the one advocating and explaining. Don’t let her feel less capable just because of deafness. She definitely can have a wonderful life, as long as she is allowed to do things differently when needed and be more visual that the hearing peers.
See also Reddit/deaf, a great forum.