Clen won't really do much in 2 weeks and if she encounters problems sleeping or high stress from it, that can just promote cortisol and water. Your choice however.
I'm hesitant to get into water manipulation in the extreme like competition prep because a day at the pool can usually include being out in the sun and drinking alcohol - both of which promote dehydration, which would really just be further aggravated by a water manipulation.
Depending on what her current diet is like, doing a carb cycle or 3-4 days of keto and maybe a quick carbup (fast carbs) or just starting back on eating "fun" food that day will be enough. If you have 2 weeks, you can also up the cardio - add in HIIT or whatever that is different from what she currently does. If you get into it more, you can do full-body workouts the last couple of days, no leg training after the prior Wed to minimize "watery" look. The full-body workouts are for the purpose of burning up remaining glycogen for a final carb load to fill out.