LWW,
When I was going through the treatments, I never let anyone in my office know about what treatments they were. They just knew I needed to go to the doctor's and was trying to deal with some medical issues. Luckily, 95% of my work was done independent of other people and I had flexible timings so the doctor's appointments were not an issue mostly.

That said, yes, there will be frequent appointments - some that you know of in advance and some unexpectedly. Most of the appointments are based on the menstrual cycle and will need to be kept on an exact day after the periods start. Lather, rinse, repeat if it does not work in this cycle.
IVF needs a couple of days of bedrest too.

For her sake, I hope your coworker talks to your boss about her treatments. It might make him more sympathetic, or it will atleast give him a chance to explain why her absences are causing a hardship to everyone involved. Maybe they can chalk out a work plan that suits everyone better. Also, if its a matter of trust, she could produce a letter from her doctor about her appointments.

b8.