All us ladies have the yeast like fungus/bacteria candida in our vaginas but it's usually kept in control but it's usually kept in control by the natural acidic environment.
When this is disturbed it can mutiply and cause problems, high blood sugar can also cause this. Understanding what is is may help in seeing ehat you can do to help it.
Have you asked your doctor if your meds for your diabetes may be able to be adjusted to stop this happening? Maybe an anti-fungal medicine as well might help.
Eating yoghurt (or a daily acidophilus supplement) can help your bacteria balance and maybe help prevent it. You could also avoid anything containing yeast.
Other possible triggers to avoid are dried fruits, dairy products, mushrooms, pickled vegetables and fruits, monosodium glutamate and smoked fish and meat.
Make sure you check any drastic dietry changes with your doctor or diabetes nurse though.
Aloe vera gel can also bring some relief to the affected area and is nice and cooling, more so it you keep it in the fridge.
Thrush likes moist spots that may be chafed or sore so maybe try keeping the area clean and cool (gentle unperfumed body washes - don't scrub, gentle -nothing perfumed and don't use those vaginal washes - and cotton knickers and avoid tights or tight trousers). Avoid long hot baths.
Antibiotics and anti-bacterial products (eg soaps or body washes) can upset the balance of the bacteria and cause them to multiply so be careful with these.
Steroids (eg for asthma or arthitis) and hormonal changes eg the pill can also upset the balance of bacteria.
Condoms may cause it if you're allergic to latex and if you're not lubricated enough and there's is friction that can set an attack off.