I'm I a bad person for this?

So I started working at a daycare and I am a floater. For those who dont know a floater is someone who gives people their lunch and closes on certain days. Well I have a set schedule as well, but not one week did I stick to my schedule. I understand the term floater, but when I see my scedule I expect to follow it. There are other floaters as well. So I have been called in numerous times and stayed when I can because people just keep not showing up to their classroom (lead teacher calls in sick and they never show up. Now we have 2 to 3 people a day calling in sick since we opened a month ago. There is maybe 10 staff. That's ridiculous. Well I only told my manager I cant stay 2 times. The rest of the time I stayed or came in early. Well today she texted and I told her I could come in early and maybe someone can replace me at my normal time to go home. She sent me a text and almost seemed mad at me for not closing. My question is am I wrong for this, I only declined staying two times and I've probably been asked to stay or come in (that wasn't on my schedule) about 6 or more times. Or should as an manager have a better grasp on her workers? I try my best I really do but when I have a schedule I expect to follow it or why is there a schedule at all?

The reasoning behind me not staying when asked (pass my scheduled time) yesterday was due to I needed to pay medical bills. Today I stay and close because of I live in one of the states that was affected by the hurricane (we got a severe tropical storm not the full thing overall my state had 13 tornado warnings) and I was planning on checking on my grandparents they where in one of the worser areas.