Not sitting up the greatest at 4 months

My baby will be 4 months on the 8th I noticed a lot of babies her age are already sitting in exersaucers and the Bumbo I'll put her in them but she slow just to the side she has good head control I can't leave her unattended is this normal? I just feel like she's behind she hates tummy time and she breaks out after a minute but we've been doing it every day she will be 4 months on the 8th and I'm just kind of concerned it might be normal on the first time I'm not sure thank you