Thanks for the replies everyone! I already have her quarantined in a gallon bowl (since last night) & have started treating her with aquarium salt & hikari betta revive. I plan to do 100% water changes daily. I've tried feeding her frozen blood worms, betta bits (pellets) & betta flakes...she doesn't go for any of them. Oh and the pics are recent, I just took them last night before moving her into the quarantine bowl.
The 10 gallon tank she shares w/Ravi has a heater set to 80ºF so the water temp doesn't fluctuate more than 1-2º at any given time. I conditioned their water using nutrafin aqua plus before I put them in their new home. Filter is a tetra whisper for 2-10 gallon tanks. No other additives to the water. I check the pH & ammonia levels daily, pH is always around 7.2-7.4, ammonia levels are always under .25 ppm and the tank undergoes a 50% water change weekly. All the plants/decor inside the tank are made of plastic except for the substrate.
Ravi, on the other hand is doing amazingly well! His fin rot is completely gone, the points of his fins have started to grow back, & his colors have brightened up tremendously! He's always had a healthy appetite since we got him & he's not picky, he goes for everything (pellets, frozen blood worms, even the flakes). He loves to swim around & he blows LOTS and LOTS of bubbles! He seems really happy and healthy so I don't think whatever is affecting Sheila is contagious, but I'm keeping a close eye just in case. Here's a recent pic of Ravi (taken last night):
Hope to get more feedback from you all soon! Any & every lil bit of info/knowledge helps & is greatly appreciated!!!