Would the charitable work that a colleague saw me doing be considered hypocrisy, even though I did not intend for anyone to see me, nor did I want her praise, but rather I wanted her to know that there is good in me and not to think ill of me?

If someone performs an action sincerely for Allah Almighty and then another person becomes aware of it and is pleased by it, this does not count as showing off (riya'). For showing off is the performance of an act of devotion with the intention of gaining benefit from people or their praise. As for people praising a servant after an action, or his joy that Allah has made his good deed manifest and concealed his bad ones, this has no effect on sincerity.