You may be able to reach a compromise between her design and how oppressive she can feel.
here are my suggestions for her ability.
"Every 'n' turns remove 2 strength from the strongest opposing non-gold unit(s), and 1 strength from the second strongest opposing non-gold unit(s)"
that n value could be 2 or 3 tuns (depends how it would balance)
what this does is:
obviously cause her to proc less frequently so as to give a bit of breathing room so to speak. (gives you more opportunity to stagger your units)
however the ceiling/levelling effect is more powerful to compensate for this.
just FYI, it is necessary in this idea for her to do -2 and -1 respectively, so she still levels the board.
or the other idea I have is: (and TH3WITCH3R also)
"Every turn remove 1 strength from the strongest opposing non-gold unit(s), that are higher than 'n' strength"
This imposes a ceiling limit, that can be 3, or 4, maybe 5 strength. although i feel 4 is the magic number, that's more or less an educated guess right now.
Once the board is levelled down to 4 strength, any further is probably too much.
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Just some ideas here, but for now i think she is a good but no OP card.