Polite way to ask friend if she needs help reading?

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I am embarassed to go out in public with an acquaintance of mine. She is at least 40 years old and cannot read or spell. I am beside myself in public when she talks like a baby and is filling out an entry form and is asking me how to spell words like mountain and spring. She isn't being funny or cute, she really can't talk or spell. She leaves letters our of words when she talks and people give us a puzzled look. She was fired from her job at a convenience store because she can't count money. She's perfectly normal, I think she likes for people to stare and whisper about her. Is there a polite way to ask her if she needs help reading or spelling?