When money is borrowed, interest is typically calculated as a percentage of the principal, the amount owed to the lender. The percentage of the principal that is paid over a certain period of time (typically a year) is called the interest rate. Interest rates are market prices which are determined by supply and demand.
Swollen nipples in dogs is a common symptom seen in mastitis. Mastitis occurs when there is an infection of the mammary glands. Mastitis is common in female dogs who are in the process of nursing. In mastitis, the dog's mammary glands become swollen and painful. The milk is toxic in affected nipples.
/ 2. I agree with Izzie that you should take her to the vet for a check up. Its difficult to tell between a cat that just has teats full of milk and mastitis if you haven't seen it before but the vet will be able to confirm what it is and get her meds if she needs it.