Diamonds are not indestructable. "The fact that diamonds are a hard substance refers to their ability to withstand scratching, but that is different than toughness, which refers to the ability to withstand breaking or cleavage. Diamonds can chip, but only a diamond can scratch another diamond." (http://famousdiamonds.tripod.com/faq.html),
So there you go Emma is not indestructable, she doesn't match up well against Colossus either. Compare their stats as gathered from:
www.marveldirectory.com/
http://www.marvel.com/universe/
http://www.classicmarvel.com/cast.htm
Emma Frost
Height: 5 ft. 10 in.
Weight: 144 lbs.
Colossus
Height: (normal) 6 ft. 6 in. (armored) 7 ft. 5 in
Weight: (normal) 250 lbs. (armored) 500 lbs.
Strength Level
Emma Frost - possesses the normal human strength of a woman of her age, height, and build who engages in moderate regular exercise
Colossus - In human form possesses the normal human strength of a man of his age, height, and build who engages in intensive regular exercise. As Colossus he can left (press) at least 70 tons under optimal conditions. (I now understand that he is 100+)
Known superhuman powers:
Emma Frost
- various telepathic abilities.
- can read minds and project her thoughts into the minds of others can project psionic force bolts which have no physical effects but which can affect a victim's mind so as to cause the victim pain or unconsciousness
- can also induce mental pain merely by touching the brow of her victim.
- can telepathically "sedate" her victims so that, if already rendered unconscious, they remain so for as long as she continues to "sedate" them. It is unknown how effective her "sedating" ability is on victims who are awake.
- is an above average athlete and has had some training in hand-to-hand combat
- can assume a diamond-hard, nearly indestructible form.
- may not use telepathic abilities while in "Diamond" form
Colossus
- ability to convert the tissue of his entire body into an organic steel-like substance, granting him superhuman strength and a high degree of resistance to bodily harm. This substance, resembling organic steel, is of unknown composition but appears to be analogous to osmium and to carbon steel. He is able to transform into this armor-like state at will (the process is virtually instantaneous) and remain in that form for an as yet undetermined amount of time. (The longest time he has remained in armored form so far has been five days). Once in his armored form he remains so until he consciously wills himself back to normal. If he is rendered unconscious, however, he spontaneously reverts to his normal form. While in his armored state, Colossus possesses the same degree of mobility that he does in his normal form
- is highly resistant to most forms of bodily harm. His armor is capable of withstanding ballistic penetration, including that of a 110 millimeter Howitzer shell. He could survive a collision with a loaded, one-ton flatbed truck at 100 miles per hour or an explosion of 450 pounds of TNT. He can survive extremes of temperature from 70 degrees above absolute zero (-390 degrees Fahrenheit) to approximately 9000 Fahrenheit. However, it is theorized that above the latter temperature, his armored form would begin to melt. Colossus's armored form cannot rust under normal Earth conditions
- has exhibited a minimal or nonexistent need to breathe while in his armored state. However, it is believed that he could not survive for long in a vacuum. His endurance and speed are somewhat greater in his armored form.
So there you go, based on the info, she gets her "albiet very nice" ass kicked rather badly.