Flawless is really difficult to work with on its own, especially if you haven't used it before.
I would say to use Intense Pink on Thursday as you don't have any time to practice and then in the mean time, before her rebalance, try out your custom blended powders to find the right mix for her, especially if you are wanting to extend her nail beds.
Edit....just reading your original post you are wanting to do a natural set.......what are the imperfections like, as intense pink, or any pink over the natural tip, won't look natural.
Would she not like them painted to cover the imperfections after you have applied the enhancements.....sorry if I sound a bit simple but I don't know how long you have been doing nails and your level of experience!