Sorry no there isnt ingame. You need to send a support case to MA. Its not too intrusive having an inactive mentor unless you want to chip, but I can see how it can be a bit of an annoyance. Just contact MA, they should be able to help!
Good luck
Frankenberry
I think if you raise a support case to MA explaining what has happened they can release you from your disciple state.
Unless you are still very new, you won't be able to get another mentor, but as far as I know, if you don't get released you will remain a disciple with the limitations of that (no skill chipping) even when you reach the graduation level in your chosen skill.
they set me free from mine back then on support-request. it took a long time till they believed me that he was inactive. i think i was at 2600 rifle when i was released.. lol