Ah, yes, I see your point. If it can't address the use, it can't define a misuse. The $7.5 million angle was always stupid, as he wielded the value of his veto, not $7.5 million, as the $7.5 million budget has no existence until it's law; but yes, additionally, if it cannot address his wielding of his veto, it can't declare a use to be an abuse.
Though if it can address what he receives, then what we have
is the soliciting a bribe:
http://www.statutes.legis.state.tx.us/Docs/PE/htm/PE.36.htm
Sec. 36.02. BRIBERY. (a) A person commits an offense if he intentionally or knowingly offers, confers, or agrees to confer on another, or solicits, accepts, or agrees to accept from another:
(1) any benefit as consideration for the recipient's decision, opinion, recommendation, vote, or other exercise of discretion as a public servant, party official, or voter;
Soliciting her resignation in exchange for his exercise of his signing discretion is soliciting a bribe.