i can only go by how i feel but sometimes the 'trying' can actually make things worse no matter how well meant.
if like me you have very low self-esteem you tend to feel that people are taking the p**s if they are nice to you or compliment you or that they are just being nice because they feel they should or even that there's a hidden motive behind it.
Icehawk sometimes gets offended or a bit annoyed with me because as he sees it if HE thinks i have a lovely body, im good, pretty, have behaved well etc then that should make me happy and i should trust him,which i know is true but it's not always that clear cut and also it is an insult to him that i dont believe him, i can see why he feels that way (because basically im calling him a liar) but all that does is make me feel more worthless than i already do...because now im failing in that area too.
im not of any help sorry, im just trying to explain how it can be from the other side so to speak,im not your girl so i dont know how she feels and how long it's likely to last.
is she generally a confident girl?it something she struggles with regularly? or is it something new to her? maybe if it's something she's never had a problem with before then plenty of reassurance and support will help..what is her low self-esteem about? herself,her looks? her body,her submissiveness? or everything? or is something in her life going badly right now?
having low or no self-esteem can be many different things for many different people and can come about for many different reasons,and until you and she knows exactly what it is she feels that is so bad about herself and she can start to work it out for herself then im sorry for being so pessimistic but i doubt there's an awful lot you can do about it. though as i said i can only go by what i know is true for me.
one thing that probably will be good for her is to keep things as usual rather than letting anything slide,even if that is difficult at times. more than ever right now she will need routines,direction and something to focus upon.if she loses that then she will lose much of what she strives for, and for somebody with no esteem or confidence they need goals...something they can achieve.