The white leaking most probably is urate. Her vent looks as if she has produced a lot of large eggs during her lifetime and at her age the tissue is just losing elasticity.
Or do you notice any strange yeast-like smell ?
As dewormer I use Flubendazole 5% , but depending on the country you live...
5 years is quite advanced age for laying hens.
This is how I would proceed:
Deworm her thoroughly
Give one tablet of calcium citrate 600 +vitamin D3 daily for 7-10 days. In the evening just grab her from the roost, sit her on your lap head facing front. Gently tug down on her wattles, slip...