It gets established somewhere that lowbloods tend to have more and better psychic powers, but, in return, they are more vulnerable to psychic powers. Highbloods are the opposite: fewer and weaker psychic powers (for all that the two examples of highblood psychic powers we have are pretty damn imba).
She definitely can't use it on anyone on Equius's level or higher, otherwise she would have after he and Aradia betrayed her. And the fact that she need to DMR to control Terezi suggests she can't even control anyone on Terezi's middle-of-the-ground level.
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"Oh God, maplejet's trying to be cool again. I'll call the ambulance." - Wylvane