That is NOT correct. The host federation has the obligation to replace a skater/team who has withdrawn. The only stipulation is that the skater/team MUST be ranked in the top 75 on the ISU
Seasons Best Scores list. The position on the ranking list is of NO consequence.
Tugba is #34 on the list, so she meets the criteria, and since she resides in Canada and is competing at Skate America the week before, she would be an obvious choice.
Bear in mind that we are now within two weeks of the start of Skate Canada. That will automatically limit the replacement choice, since it's probably too late for many skaters to get visas and travel arrangements in time.
Your entire concept of how skaters are chosen for GP events is wrong. The host federations draw for selection order, and for selection order only. Then each host actively selects skaters for its event, according to ISU rules. Each host may choose 3 skaters in each discipline from its own skaters. Then each host must choose two seeded skaters, then two skaters from the top 24 on the ISU Ranking list, then two skaters from the top 24 on the Season's Best Scores list (other than the ones in the top 24 on the ISU ranking list). The rest of the skaters are chosen from the top 75 on the Season's Best Scores list.
The hosts select the skaters according to ISU rules. If you want to see the rules in writing:
http://isu.sportcentric.net/db//files/serve.php?id=579
Look in Section 2
DESIGNATION OF THE SKATERS, 2.2
Invited Skaters/Couples