Yeah I can imagine that. Great to see that you're open for suggestions :)
Speaking of which, I have a few other suggestions for you. 

How about the flow of time in Umbra works differently from that in Azukhar? That way, we could say that Morgan is... Let's say 25 years old (your call of course), speaking in Umbraïn time and appearance, but dissappeared from Azkhar as a child around 250 years ago. Basically, it would mean that she hasn't aged as much as she would have on Azukhar. That way she (yep, I'm just sticking with the 'she' even though Morgan is genderless, just for the sake of being practical xD) wouldn't know a thing about what's going on in the world, have no family members or connections on Azukhar and she won't have an idea where she came from or if that place even still exists. Moreover, spending 250 years in another realm would make her completely alienated to Azukhar and would make it very likely for her to become twisted in a way that she's barely human any longer. I suppose she could have gotten stuck in Umbra due to a previous wielder of the key. Figuring out how on Azukhar that happened is up to you (if you're going with this idea lol).

Another option is that as soon as she entered Umbra for the first time, she lost her memory, or she was too young to remember anything about her time on Azukhar. 

As for Morgan's clothing, I think tights and a top or simply a closed cloak will help a lot to get rid of the undergarment feeling, without having to lose much of the sex-appeal (I suppose you made the picture yourself? If not, I can totally understand that even small changes will be rather hard to do.)

All of these are suggestions, so feel free to ignore or incorporate them :)