i'll try one more time and if you cant understand me then that's fine and i'll let it go.
lissandra is an organic being that can create ice and then move it at varying distances.
in order to move something without contact you have to have a gravitational pull (a dense object) or a magnetic pull (which involves polarity) or like you said a vacuum - which is the absence of something (usually a gas) being filled by the presence of something trying to expand to fill the emptiness left from the absence of the something.
if she has a gravitational pull that she can control then she would have to be able to change her density.
if she has a magnetic pull then she'd have to changer her polarity.
if she creates a vacuum she'd need to first create the vacuum and that would be harder at long range.
each of those 3 things have their own issues as to why manipulation of a single distant object would be either impossible or difficult.
but if she could somehow not only control her own density but the density of the world around her, the polarity of the world around her, and then of course create vacuums through those types of interactions she could control things and cause them to move independently of their surroundings.
secondly in order to freeze things while keeping them organic youd have to subvert the laws of sublimation and resublimation. otherwise it would cause state change.
you're not freezing the object but rather the water around the object in the air. that's why cryogenics is a complex subject... because in cryopreservation if ice crystals form then effectively you've just killed whatever you tried to preserve. cells rupture when ice crystals form.
basically air pressure and humidity are very important to lissandra.
she could then somehow scatter energy from her area and cause an anomaly of ultra cooling.
the area outside of her immediate person though would be like standing next to a radio tower on full blast
