A midwife asks a gentian violet solution for thrush in babies and an ointment for breastfeeding mothers.

the concentration used is 1%. But the solubility of Gentian Violet in water is about 0.67%. Consequently, the solution is usually added to alcohol, but for the requested application this seems difficult to achieve. But Gentian Violet also seems to be well soluble in glycerin (1 to 30). So maybe 1g gentian violet dissolve in 30g glycerin and dilute this solution with water up to 100ml.

apparently stood a gentian Violet ointment described in an old edition of the NF. There are 2 strengths: a weak = 0.5% and a strong = 1%.
is used as an ointment base: ZnO 20g; starch 20g; wool fat 20g; Vaseline 20g and lime water for the weak 19, 5g and for the strong 19, 0g.
Another possibility may be the use of PEG base; if too consistently increase the level of PEG slightly 400.