Tiger Woods split from his ex-girlfriend is way nastier — and potentially more expensive for him — than we thought … TMZ Sports has learned she’s suing him for $30 million, claiming he cooked up a scheme to toss her out of their home.

According to docs we’ve obtained, Erica Herman and Tiger actually broke up last fall. The then-couple had been living together in his Hobe Sound, FL home for 6 years, during which time Erica says she performed “valuable services” for Tiger in exchange for living there rent-free.

She admits she doesn’t have that in writing, but refers to an “oral tenancy agreement,” which was supposed to last 5 more years after their split.

About that breakup … Erica claims Tiger’s people convinced her to pack a suitcase last fall for a “short vacation” — without Tiger — and drove her to the airport. Once they arrived at the airport, she was told she’d been “locked out” of the house and could not go back.

In the docs, Erica alleges one of Tiger’s lawyers even met her at the airport with a proposal to resolve any outstanding issues between Tiger and her. She also claims they confiscated more than $40K in cash she had at the house, and accused her of doing something shady to get the money.

She’s suing Tiger’s trust — the titleholder on the house — for $30 mil because she claims that’s the “reasonable rental value” of Tiger’s house for the 5 remaining years on their oral agreement.

Tiger’s trust filed docs in response to the suit, and said Tiger had broken up with her and asked her to leave the home, which he shares with his 2 children. The trust denies there was ever any oral agreement about her living in the home … instead, Tiger’s team says she was only there as his girlfriend.

Basically, once the relationship ended … so did her right to live there.

Erica is also asking a judge to declare the NDA she signed unenforceable. She says federal law allows her to speak out in cases involving sexual misconduct or harassment — but, so far, she hasn’t specified what he allegedly did.

TMZ