Hey Snowflakes,
It sounds like you need to get some things sorted in your relationship with your teacher! You're an adult, paying her to perform a service for you. She doesn't get to tell you what to do. If you want a digital piano, you go and buy one! If she flares her nostrils momentarily in revulsion, that's her problem, and a very minor one compared with the inconvenience that having to play an acoustic is causing you and your family! (And, you don't actually have to tell her. She will never know.)
There's a lot of snobbery in the piano world, just like the people who'll swear that 192 kbps mp3s are nowhere near good enough for their £10000 audiophile system, when in fact it's been proven that no-one can tell the difference between them and CDs. You just have realise it's usually the result of prejudices, insecurity and fragile egos, and learn to ignore it.
Modern digital actions are more than good enough for practicing on, and absolutely will not damage your technique. Rachmaninov used to learn whole concertos on some old portable keyboard which didn't even produce any sound, when he was on tour. See
this video with Robert Godfrey about the V-piano (he talks about the action from 4:45). Acoustic actions are more different from each other than they are from digitals, so you'll get the same problems moving between an acoustic practice instrument and your teacher's piano.
I personally grew up playing a poorly regulated acoustic. I wish my parents had spent half as much and bought a decent digital, as the action would have been much better, and being able to practice any time of day or night without annoying anyone else is a huge bonus. I'd be a much better pianist today.
