She's part of TSS by default whether she attends a meeting or not.
She doesn't have to complete the YLQ if she doesn't want to but if she does then some will be carried forward to the ALQ. Whatever happens she cannot be an adult Leader until she is 18. If she doesn't do the YLQ she'll have to do the full ALQ but can start and get it completed just after she's 18.
Hi, she can work on, and be awarded the YLQ (optional to work on) between the ages of 14 and 18 (while she is a YL). If she is 16-17 she can be working on the adult LQ, can complete it before turning 18 but CANNOT be awarded it or considered a qualified adult leader until she is an adult (18).
If she does the YLQ, it all counts towards the LQ if she chooses to progress to that, but she can do one, both or none if she chooses. If she is working on the LQ when she turns 18, she becomes a Leader in Training, if she doesn't work on it, she becomes a Unit Helper. If she's completed the ALQ before turning 18, once 18 it can be presented and she can be a Leader or Assistant Leader as appropriate