Bettas, on occasion, do brew weird growths on their bodies. Usually they are tumors, many of which are not malignant and will not kill the fish. Do they hurt? I do not know but I do not believe so. At least no betta has ever complained to me about it before
. Since the bettas affected appear to maintain a normal life (swim around, eat, etc..) I assume they are not in pain. usually a fish that is sick or in pain will not move around much at all. The way I would go about your fish's tumor is probably add a bit of antibiotics for 2 weeks to see if it makes any difference. I would probably go for Spectrogram, just because it is both gram positive and negative, so can cover a gamut of bacteria and it also hits fungus as well. If after 2 to 3 treatments (so about 3 weeks in antibiotics) the tumor has not changed at all (zero, nada), then leave it alone. Either way there is not a whole lot you can do about it. Do NOT attempt to remove it! That would be your betta's demise. You would kill your finned friend trying to fix something that might not even really be broken.
I dont want her to die 
Im so sorry to hear this, but lets hope its no tumor hope she gets better soon 
