Many children with language disorders have difficulty asking for help.
I think they get used to going through life not always understanding what is said to them (if I had to sit through a physics or chemistry lecture, I would not expect to understand and so I would not ask questions). Many develop strategies to cope with this - maybe watching what others do and copying, messing around, switching off.
I did a summer group once specifically aimed at this. We had 12 children attend everday for a week. One of the aims was for them all to be recognising when they did not understand and then to be able to ask for help.
This is a huge area to work on. Reasons for not understanding could vary from - not hearing what was said, not understanding a word that was used, not remembering the whole sentence, etc.
So, in the group, we talked about what you could say if you wanted someone to help you, brainstormed sentences you could use and then set up situations, throughout the week, where they would not be able to do something we asked and so would have to ask us for help e.g. asking them to draw a picture and giving them no paper, telling them to go into another room when they would not be able to reach the door handle, giving them broken pencils, telling them to help themselves to a biscuit but giving a tin that was almost impossible to open.
By the end of the week, they were all able to ask for help in our sessions.
So, in a situation where you think she could/should have asked for help, try stopping her and modelling to her what she could have said to you e.g. ''mummy please will you open the biscuits'. Get her to repeat it to you, you then open the biscuits.
Try role playing situations as a game and you can model questions she could ask. Either play the roles yourselves or use little dolls to be the people.
Sorry for the ramble but I hope it is of some help.
I'm sure your slt will give you other suggestions.