Sorry haven't read whole thread - I may repeat someone.
At our school the SN teacher ALWAYS asks parents about their childrens crawling. It doesn't necessarily follow that if they don't crawl they will have dyslexia / dyspraxia, but it seems that many ch who have dys didn't crawl. I'm like you, I was desperate for dd to crawl just because of this reason. Everyone I mentioned it to thought I was stupid, apart from the SN group. Crawling is hereditory I think i.e. dh disn't crawl, so dd may not have.
dd didn't crawl until nearly 9 months and now theres no stopping her. She also HATED tummy time and was able to stand for months before hand.
Don't worry about it, keep making tummy time fun, pull silly faces at her and so on when you put her down, and she probably will when she is ready to.
If you are really worried play lots of games where she 'crosses the midline i.e. her middle' with her hands and feet - if you can imagine the crawling action when lying on your back. Touch hands to opposite feet, hands to opposite knees / ears etc.
Hope this makes sense. Don't worry just yet, she is still very young to be crawling.