In all honesty, pretty much every desert map comes with tight UP requirements or with other units that need to be placed first. I wouldn't level her for that kind of niche role when most of the time you'll want to place something else. Especially when her UP cost is rather high.
To put it like this: Anything a desert map will throw at you will either be so weak that a soldier can handle it AND give you UP regen, so strong that it needs a healer + tankiness, or require magic damage. In either of these cases she's rather useless.
Invest in her for stun immunity or collection purposes or because you really really want to use that specific unit for some reason. But if you want to invest in her for niche availability you're more likely to be going to burn yourself.