Can find Ronda at the park, either at the running track or by the "wander around" option.
There is more to Olivia after that. Keep visiting her at the maid cafe and ordering desserts from her, until Gemini says she isn't there. Next place you find her is at the park, wandering around; then the next time she goes missing you find her by randomly exploring the city. Should be an option to give her the sandwich after that; next time you find her after giving her the sandwich is in the mall bookstore. Visit her one more time at the maid cafe and she'll be at max weight.