Sorry I'm getting into this so late.
They are being totally unrealistic, but they are ignorant. You and your daughter need to set their expectations appropriately.
Tell them that they need to make sure she checks before entering the water.
And they need to have a scheduled blood sugar test for her at 45 minutes.
And they need to understand that she will also need to be able to stop and check any time during practice if she doesn't feel right, with no repercussions. It is not a mistake for her to check her blood sugar and find out it is fine. It is a learning experience.
She needs guidelines on what to do at different blood sugar levels at each of these tests. Sometimes she may just have to break off her training sessions if she's too low.
Here's a quote from an interview with Gary Hall, Jr.:
Q: How do you accommodate diabetes and how has it affected your swimming?
train eight hours a day, with four practices. My mornings include dry
land exercise, such as jumping, running, medicine balls, followed by
swimming practice. In the afternoon, I lift weights and swim. As I get
closer to the meet, I won't train as much, because it is exhausting and
I want to have the energy to race well.
I do have better control, but some of the problems come with the
training. There's the inconvenience of being interrupted during long
swimming practices—I'll have to go out and test my blood sugar and make
sure that I'm not going too low. Sometimes I'll have to eat something
in the middle of practice. I just have to be constantly aware of my
diabetes. When I'm practicing for eight hours a day, that often means I
have to get out and check my blood sugar.
Varying accounts of Jay Cutler say that he tests "about 3 or 4" times a game, or "up to 6" times a game.
Your daughter is training to swim in school meets. It's not like she isn't stopping and starting all day.