How do I appear offline to one person on Facebook messenger on iPod?

[BubbleandSqueak]

Okay I know how to appear offline on my computer (choosing appear offline and selecting who you want to appear offline to) but I'm not sure if it works on my iPod?
I selected the appear offline thing to one person on my computer and they didn't talk to me (they usually do all the time ) so I assumed it worked and they thought I was offline. But even though I had selected this, I was talking to a friend on my Facebook messenger app on my iPod and they started talking to me. I thought it would work on my iPod too but I don't think it does because they talked to me on two different occasions whilst on my iPod. Help?
I know it seems mean to want to appear offline to someone but they are really annoying! I could just un-friend them but that seems too far because they are my friend, they are just quite annoying (and not in a close-friend-it's-okay kind of way).

[Daniel]

You Cant Do it From the App The Only Way to Do it From your Ipod Would be to Use the PC Site and Set it to Appear Offline For That One Person

[Drizzy]

You can't do that on mobile, but you can turn off notifications for that person. Tap the "I in a circle" icon next to their name and you will see the part where it says "Notifications On" tap on that and hit "Turn off"