Is this a red flag?

[kidlove]

I wouldnt really be too concerned, they may be dragging their feet and may also be very cautious regarding illness, either way you are getting paid. As long as they are paying, I would say...your ok. But I totally see your point of view, maybe next time you talk, you can just explain to them that she does need to start on a regular schedule or you may have to offer the spot to someone else, given you want your time "used" rather than paid for and "un-used". Are they paying full or are they getting a discount for the unattended days?

[Littledragon]

Are they paying full or are they getting a discount for the unattended days?

They only just started. I charge for two weeks prior. Since they started in a off pay week, they only had to pay for one week. So last week, when they signed, they paid for this week. So they've paid up in full