You think the Queen is an authority on time travel?
After she cocked up First Contact like a rank amateur?
Besides, some times stuff disappears like in Time Squared or Time and Again, and sometimes it doesn't like in Yesterdays Enterprise of Futures end.
But if the Admiral was going to disappear, it would have been the instant that her past became impossible, which was the very instant she met her younger self and after that one moment, her existence just compounded into becoming more and more impossible after that, not that degrees of impossibility mean much since the paradox held and it was going to continue to hold because the forces moving against it were countered or irrelevant.
I say countered as in kathryn may have been using technology to moot the paradox like a time stabilizer from babylon 5, or the time travel process she used may have inoculated her washing the old in useful radiation, or as I said before: leaving the universe/going out side of time, or becoming temporally shielded from time, means that time loses track with who you are and where you're from because of the break you took from being it's bitch. Time is lazy.
Temporal shields are the same as being outside time?
Does that mean that when you are temporally shielded that you don't age?
Did Year of Hell Kathryn discover/invent immortality and not notice?
Would she have killed herself at the end so readily if she knew she had the next ten million years to deal with Annorax Casually?
One of Christopher's temporal investigation novels claims that the notion that being outside time retards the ageing process is bosh. That it's probably just some metaphasic radiation released ambiently during the process of being some place so god awfully weird.
Like how you shouldn't drink water in Mexico, but the other way around.
Are Mexicans told to drink as tap water as they can when they holiday in the states, or are they also told to stay away from yanky tap water because it contains far less nutrition, calories and insect meat.
A gallon of Mexican water a day might be as nutritious as four MacDonalds Cheeseburgers if you can keep it down.