What do you do to get rid of your feeling of guilt for thinking that you caused embarrassment to other female Qur'an memorizers by distributing more distinctive sweets at the Qur'an completion ceremony?

The اصل (default ruling) is the permissibility of spending and giving to feed those present at a celebration held in gratitude, without believing it to be a Sunnah (definition) or for the purpose of showing off. If spending is permissible, then there is no harm in each female memorizer bringing what she can: the one with little brings what is easy for her, and the one with means can give more, without showing off, in accordance with the Almighty's saying: "Let a man of wealth spend from his wealth, and he whose provision is restricted - let him spend from what Allah has given him. Allah does not burden a soul beyond what He has given it. Allah will bring about ease after hardship." Thus, varying expenditure according to ability is permissible, and criticizing it is a trait of the hypocrites.