As someone who's also shy and has social anxiety issues, I can see how your friend might have just been shy, but on the other hand I would hope they could at least manage a 'thank you' and a smile. I have social interaction problems but I know it and I know how I can come off, so in your friend's situation I would be trying my best to let the other person know that it's not them, it's me and I really was having a good time. Posting like there was nothing wrong and it was a great visit afterward seems weird too (especially inviting you to come visit her -- maybe it's just me because I think I'd have problems with it, but that doesn't seem like something a person who's so shy they can't even say 'Thank you' would do).