Hello, I was checking the UESP for a solution to my problem and I read that there's a circumstance in which you're unable to receive the quest. This happens when you are doing a quest that opens an "indisposition" and if you finish this quest, you can receive the "grymsever quest" from her. But, unfortunately, with so many quests already on my to-do list, it is impossible for me to prove this as there are so many variables.

Does anybody have a solution to this?.

finish up your spare quest do at least 10.

Yes I think you have to be at a sufficiently high level. Keep checking with her.

She's nice to talk to anyway.

I think if you tell her your into the thieves guild she wont want anything to do with you but waiting a week or so in game will make her forget and ask for help with grimsever...at least thats what happened with me

^ This.