Reddit reviews Rachmaninov - Concerto No. 2 in C Minor, Op. 18: 2-CD Set Piano
We found 2 Reddit comments about Rachmaninov - Concerto No. 2 in C Minor, Op. 18: 2-CD Set Piano. Here are the top ones, ranked by their Reddit score.
I can't speak to its quality, but this fits your criteria: https://www.amazon.com/Music-Minus-One-Piano-Rachmaninov/dp/159615005X
Just in case you don't already know, you can find pretty much any classical piano music for free at imslp.org/wiki. It is nice though to give music as a gift. One possibility you might consider is a "Music Minus One" type CD/Score - they are recordings of just the orchestra parts of concertos that allow pianists to be accompanied by an orchestra. This would be my choice - it's just about the most "romantic" of all the piano concerto repertoire. It's pretty difficult, but I reckon with 10 years of lessons under her belt she'll be able to roll up her sleeves and have a go - it would be a nice challenge for her. Alternatively you could try to find out surreptitiously what her favorite piano concerto is and get the Music Minus One CD for that instead (if it exists).