Facebook mobile messages problem

I have a problem with the facebook mobile notifications of facebook messages. I have one friend (and she is not a "limited account" or anything like that) who when she sends me a facebook message, it does NOT come through to my phone, but everyone else's does. I've tried re-adding her, disabling fb mobile and then re-enabling it. Nothing seems to be working. I don't know if this is my phone being odd, but I think thats quite unlikely as all other fb messages come through.

Any suggestions will be really helpful guys

Thanks :)

[edit: It now seems to be happening to two people's messages :/ ]