Well, I'm currently playing a Iroh inspired Monk alongside a Zuko inspired Monk so....
Do you want Blindsight or Tremorsense?
TREMORSENSE said:
A monster with tremorsense can detect and pinpoint the origin of vibrations within a specific radius, provided that the monster and the source of the vibrations are in contact with the same ground or substance. Tremorsense can’t be used to detect flying or incorporeal creatures. Many burrowing creatures, such as ankhegs and umber hulks, have this special sense.
'Cus Toph most definitely has Tremorsense! (Actually she has far more than that at times)
I don't know of any player method of getting Tremorsense, it's mostly in the hands of monsters. but 2nd level warlocks can pickup the Devil's Sight Invocation (
"You can see normally in darkness, both magical and nonmagical to a distance of 120 feet")
Which is considered a powerful ability when combined with magical darkness, but one that already exists by the core rules.
So I wouldn't worry too much about putting such things in players hands... since something similar with far fewer drawbacks can already can be put into their hands.
There will be a handful of occasions where Tremorsense will be superuseful... esp if you rule that it lets her see though walls!
And lots of times only being able to "see" a few hundred feet will be a issue.
Also colour and reading and similar become very problematic.
Does very much depend upon what stuff actually happens in your games, in mine we very rarely actually go into dungeons or similar.
At the end of a day, RPG's aren't really balanced, it's either an aspiration or outright lie we occasionally like to use. I'd give her Tremorsense and let her have fun!