I am a speech therapist working with a little girl on /s/. She is able to produce /s/ in isolation and can even produce some /s/ blends such as "st", but when the /s/ is placed with a vowel behind it she adds an /l/. ex. "sun" becomes "slun". I have educated her and she is aware that she does this. I have provided her placement cues. We have tried to "stretch out" the words or "smash them together". I've tried minimal pairs as well. She can't even produce sa, se, si, so, su w/o the /l/ added. I'm at a loss. Any suggestions are welcome.