It sounds like she's feeling insecure because of all the change, so she's clinging to you, wanting to be with you and scared of what might happen while she's away.
I am a bit of a soft touch, so if I wasn't working I'd maybe give her a week at home if the refusal was severe enough - and just try to let her breathe and relax a bit - do some relaxation stuff, chill her out. However this could go the other way - she might hate the idea of going back.
Is she worried you're going to die? Was she close to the family member who passed away? Was it sudden or expected? Has the new baby impacted her life and routine?
If the new baby is in her immediate family this is totally, totally expected. Mum's at home giving all of her attention to someone else. Is she getting enough special/quality time alone with you outside of school?
Maybe you could try some rewards for attending without issues, such as special things you can do together - eg if there aren't any problems on Monday morning you'll make a cake together Monday night, or get a DVD to watch just the two of you...