Not to be persnickety, but YOU don’t ask her to fast? Don’t you think that’s up to her?
I get up at 7 or 7:30. I don’t choose to eat before Mass, but if you’re Mass is at 9am, you’re not likely to receive Communion until at least 9:30 or so. There’s plenty of time for breakfast and fasting for 1 hour in that time frame. If she feels up to singing during the pregnancy, she should sing. I worked at an answering service, went to college and taught ballet during my first pregnancy and had very easy time of it, including a quick delivery. A friend of mine taught a gymnastics class ending at 7pm, and her baby was born around midnight. Your wife and her doctor know what’s best for her.
In Lent, she’s not required to fast, but she can still abstain from meat. She won’t sick if she eats grilled cheese and tomato soup or scrambled eggs on Fridays. Is she allergic to fish? There are only 2 days of the year we’re asked to fast, and I think that only the most extreme of circumstances will excuse anyone from those two very small sacrifices.
She can make this work if she wants to, but let her make her own decisions about it. She knows what’s best for her body.