Thank you for the additional information.
Without doing some testing it would be impossible to say for sure what is going on.There are several things that can cause this problem.
* Ear mites.
* Fungal or bacterial infection.
* Fly strike which is caused by fly bites on the tips of the ears.
* Ear vasculitis ( more common in dogs but can occur in cats
* If the tips of the ear are white this could be due to sun burn, this can result in skin cancer and in some cases the tips ear needs to be removed.
* This could also be due to fleas so be sure you are using a veterinary approved flea product such as frontline or advantage now that she is spending more time outside.
I hope this helps, please reply back if you have additional questions or concerns
I would suggest having your vet look at the ears and perhaps do some tests to look for mites, bacteria and fungal infections.
Until you can have her seen I would clean the tips of the ears well and apply neosporin