Poor little thing
I reccently lost one of my robos to a really bad tumor but it was under her front leg and inoperable. The first thing you should do is get her to a vet, they will try and perscribe antibiotics (baytril) and may say to put her on it for a week/2 weeks and see how things go but inquire about the possibilities of removing it as its appears to be on the outter ear it may be possible
I only ever cleaned Cookies tumor with warm salt water when ever it bled and its seemed to work well, keeping it clean did help though so carry on doing that bit yourself. Also keep her claws cut so that she doesnt scratch at it and make it bleed more, or worse infect it.
If for some reason it is inoperable then the best you can do is spend lost of time with her. In the worst case sceanrio you may have to chose to help her along eventually if the tumor starts causing her problems. This was the decision I had to make with Cookie as she could no longer walk and was in a lot of pain, however she did live three months happily with it so even if it does come to this you may still have a lot of time left.
First thing is first thoug, before you worry about anything like that get her to a vet and see what they say. Its not always as bad as you expect. Good luck