Even though Timatic has an option for TWOV listed, she will not be allowed to board ex-BOM without a visa for the UK so you can forget about that option. She will need a visa.

One issue that may crop up is if your wife has her US address listed in her Indian passport. In that case they may insist that she applies to the British Embassy or Consulate in the US rather than at any of the Indian posts since she is resident there. I had this problem in 1998 when I last applied for a British visa in India (with my US address listed in my Indian passport) and eventually had to get it done through the Consulate in New York. I have subsequently obtained a second Indian passport that lists only my India address to avoid a similar problem cropping up (many countries have this insistence nowadays on lodging applications only in country of residence). If only her Indian address is listed in her passport, then she won't have a problem.