What is the ruling on a woman praying in her workplace where her male colleagues might see her, and is she obligated to make up the prayer if she cannot find a secluded place to pray?

Prayer must be performed on time. The presence of non-mahram (definition) men does not prevent prayer; rather, you must cover yourself during prayer, even if they look at you. It is not permissible to combine two prayers except out of necessity, such as travel, fear, rain, or need.