DD7 is very assertive with us at home and very confident. A bit defiant, a bit rude for no real reason.
Outside home, particularly at school, she is absolute perfection, kind, considerate, easy going to the point of being taken for granted and she ended up being bullied severely by someone who was her best friend. This little bully has left her school so she's recovered from that.
She's made a few new friends now but I can see she has very little confidence about herself. She's always the one giving in, she overly nice and gets a bit bossed around. Today her 'best friend' was a bit bossy so she's upset about it.
Not sure about SEN but I suspect there is something mild to consider.
Can things get better? Can you teach assertiveness to kids? I don't remember being like that at her age and certainly I wasn't allowing anyone to bully me or boss me around. I know she just wants to be happy and play with no issues but a lot of the time she has to be the one putting up with unkind behaviour.