You should be proud! That's a terrific achievement!
My DD is almost 9 months old. I'm so proud of myself for sticking out breastfeeding this far with all that I've been through!
It sounds like your baby needs more milk. If she's sucking down big bottles of formula then more than likely the solids are not cutting it for her. At less than 1 year, milk or formula provides all your baby needs- solids are just for fun, they're not nutritionally necessary- and many babies do not graduate to a majority-solids diet until well into their second year. Milk or formula also provides a more balanced diet than most solids, so it's preferable in that way, too.
It sounds like the only thing holding you back from providing more milk is the people you work with. Don't feel like you need to explain yourself to them. Your primary responsibility is to your baby, not to your colleagues' and their uninformed opinions. You could, however, think of this as an opportunity to educate your co-workers: none of them have kids, but you have the chance to show them how to give their future babies the best!
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"