On the note of your daughter being told off, that wasn't the case. She was asked to not use text speak like everyone else. I can certainly understand a learning/reading/writing disability. And no one here knocks anyone for having one. We do not single people out to "pick" on, nor do we discriminate against those with known issues.
Whether the Dyslexia be Trauma (injury), Primary (hereditary), or Secondary (hormonal) the person with the disability is not in any way completely helpless. And as they are taught how to work with their disorder, they are shown how to compensate and develop good coping skills. Since often in the real world and in the job field many will not accept I'm dyslexic as an excuse for not stopping at a stop sign when driving, or messing up on a job you agreed you could perform.
Most dyslexics do have issues with spelling, reading and even sometimes speech. But when anyone can replace a word with a single letter or number with typing as they should in text speak, then that is indeed what it is "text speak". Often people use text speak out of having to cram mass amounts of words into a small space as such with cell phones. In the chatter this is not the case, you have plenty of space. As a dyslexic "yuo jus mit mes up yur spelin", but " 2 replace words 4 num3ers or leters is just laziness on ur part". So bottom line if it is misspelled and when asked you say I am dyslexic then ok we understand and can help you accordingly. But when you use actual text speak, then yes you will be warned like everyone else.
As for solutions, there are browsers with built in spell checkers; such as Firefox, Google Chrome, Konqueror and Opera. There is an Instant Messenger client called Pidgin that has one built in for your IM needs. All Mac OS systems have a spellchecker built in system-wide. And I have two spellcheckers here, the first is free and download-able it can be used with any application:
And this one is online, you can type out entire im's, documents, etc.; check them then copy and paste them elsewhere. And you don't have to download it:
I hope this helps, and clarifies what is up to the user to correct, and what we as Moderators are responsible for.