Tuition carryover credits are tracked by CRA and they will apply them at the earliest possibility. If you connected to the relevant CRA accounts then you have the most recent information available. If there is an error, they will correct it on the Notice of Assessment.

As you noted, you can transfer tuition credits to parents. Generally, and I mean this as more of a social statement, this is only done if a parent paid tuition for the student. Assuming they’re in a higher tax bracket, they will get a bigger return for reciting it. Some parents give that money to their child, though most just bank it for themselves. I’m unsure if a parent can carryover tuition credits that are transferred to them; I’ve never seen that situation personally. If your sister didn’t transfer the credits, then it will be carried over for future years. If you have the previous year NOA, you can see what the carryover amount is (the same as CRA has).