So I've been considering Hollie's power for some time and I don't exactly like Density manipulation. It is not "eye-catching" enough. So how does this sound as a replacement?

Hollie can spontaneously shapeshift into a translucent crystal form. While crystallized, she is resistant to physical damage, packs a harder punch, and can absorb energy to supercharge her form.

    Energy Absorption
    While in her crystal form, and only in her crystal form, her touch can draw energy from various sources. Electricity provides the greatest amount of energy but absorbing energy from another being can yield energy. This gives Hollie a sort of Vampiric touch and allows her to drain energy from her opponents at relatively a slow rate. Another method of energy absorption can come from a sort of energy "rebate" when Hollie receives kinetic strikes (punches, bullets, etc.) to more Meta energies (beams, blasts, etc.). Even though she may benefit from being on the receiving end of an attack, her crystal form cannot take a lot of abuse and may crack and break causing real injury to Hollie's actual form.
    Supercharging
    A surplus of energy stored can be used in various offensive or defensive strategies. Hollie can use built up energy to rapidly grow pillars of her crystal material in an attempt to impale or block an attacker, project an energy beam, and as a final resort, explode out from her crystal form using up all energy she had in stored. Some synergistic strategies can be thought of by using a combination of her powers. Any crystal pillar will also be energy absorbent and by blasting the pillar with energy it can reach a break point and explode.
    Weaknesses
    Outside of her crystal form, Hollie is vulnerable. It takes her awhile to build up enough energy to use her extra abilities, before that she is just armored. Her crystal form can be damaged and eventually destroyed. Her crystal form can be pushed to a volatile point by rapidly adding too much energy, causing Hollie to explode.