with the blessing of time, couldn't she have froze him and escape??
How would she do that?
She is in a heavily guarded place, with many check points.
Even if she manages to puts him in Time Freeze, she would have to escape the Church and then the City.
But considering the situation, i doubt she would be able to put the Time Freeze spell on him easily, as I am sure there are many restrictions on its usage.
Which is the real question, isn't it? What are the extents of her powers, and the restrictions?
Depending on how powerful she
might be, a localized version of Jojo/Time Stop Brave is one method, by essentially going "Za Warudo!", albeit most likely in a more localized space.
There's also another manga, The Time Mage's Strong New Game, where his abilities essentially make him OP, but that would require a certain mindset to begin with. Rukia would need to have the willingness to fight with the intention to kill, and have the mental imagery to shape her magic in manners that she would be able to use them in combat. Depending on how her powers work, never mind freezing him, she could potentially age him into dust. Unfortunately, she doesn't seem to have the personality for it right now.
For the time being, it's somewhat understandable that she's taken aback. Given time, and how angry she might become for knowing the truth about the Inquisitor, that mindset may change,
if she can make herself believe that her brother can still be saved. If she already believes them to be dead, the only thing she can do is focus on her self-development, and on her escape. The problem then becomes, where can she go when she does? Which will also restrict her actions, unlike Rosa who had absolute faith that the people of the Church, including the Inquisitor, were all good, until she was thrown away.