Learn English – Can you describe someone as luxurious

'Two sides of the same coin' does not quite mean what you describe.

two sides of the same coin - different but closely related features of one idea

It essentially means that two things are the same. I might use it in a context where someone is describing someone else as both 'lazy' and 'messy' and in response I could say that those are 'two sides of the same coin' and thereby suggesting that they are one and the same, in this case suggesting that the person is messy because they are lazy.

As far as I can tell you want a pithy phrase to describe two things that are good together but not necessarily either good or as good apart.

I'd suggest a simile in this situation. A very common type of phrase is to say:

[Something] without [something] is like [something else] without [something else].

Currently on the London Underground for example there is an advert that says something along the lines of 'a woman's hair without product x is like rock without roll' (the latter part usually a ridiculous separation for humour value). There's no standard phrase used here but it's an opportunity to be creative.

A couple more examples:

A man without ambition is like a bird without wings (from a 1908 business magazine)
A house without books is like a room without windows (a proverb that goes back even further)

• She is "accommodating". She is eager to fit in with whatever you suggest. http://www.google.com/search?q=obliging&ie=UTF-8&oe=UTF-8&hl=en&client=safari#hl=en&q=accommodating

• She is "affable". That is, she tries to get along and not make a fuss over anything. Opposites might include "argumentative", "contrary", "difficult" (no matter what you suggest, she suggests something else, as if she were being opposite just to be opposite)

• She is "amenable". This is similar to "open"; she can accept any idea or plan. (often "open to _____" or "amenable to _____") http://www.google.com/search?q=obliging&ie=UTF-8&oe=UTF-8&hl=en&hl=en&q=amenable

• She is "complaisant" (not to be confused with "complacent") http://www.google.com/search?q=obliging&ie=UTF-8&oe=UTF-8&hl=en&hl=en&q=complaisant

• She is "deferential". That is, she accepts your wishes or judgment—to be polite (out of respect for you). Opposite might be "overbearing" (imposing her decision on you, regardless what you think.)

• She is "flexible". She can adapt to any situation. Perhaps she really doesn't care. Opposite is "rigid" (with very specific, unchangeable ideas of what she wants or would agree to)

• She is "obliging". That is, she wishes to please you by doing what you want to do. http://www.google.com/search?q=obliging&ie=UTF-8&oe=UTF-8&hl=en

• She is "pliant" (easily persuaded or influenced) http://i.word.com/idictionary/pliant

• She is "tractable" http://www.google.com/search?q=obliging&ie=UTF-8&oe=UTF-8&hl=en&hl=en&q=tractable