BALTIMORE (AP) _ A Filipino immigrant who operates four restaurants called ''Sony's,'' after her nickname, has lost a fight with Sony Corp. and must change the name of her businesses.

Sony Corp., the giant Japanese electronics firm, filed a $2.9 million trademark infringement suit against Resureccion ''Sony'' Florendo for her use of ''Sony's'' as a restaurant name.

Ms. Florendo said she has used the nickname ''Sony'' for most of her 51 years and that it has been common in the Philippines for decades.

But in a consent decree released Monday in federal court, she agreed to change her establishments to ''Sony Florendo's.'' The name change must appear on menus, napkins, stationery and advertisements by Aug. 19, and on external signs by February.

By March 19, 1991, she must remove her nickname from all signs and advertising.

In exchange, Sony Corp. agreed to drop its lawsuit charging that Ms. Florendo's use of her nickname on her small Filipino-Asian restaurants constituted ''willful infringement and acts of unfair competition,'' that diminished the value of the corporation's worldwide trademark.

The company had argued when it filed suit last November that it has been using its trademark name since 1955 and that Ms. Florendo had been using her name on restaurants only since 1976.

Sony Corp. has now acknowledged that Ms. Florendo, her husband and business partners ''acted in good faith when they adopted and used the name 'Sony's' in connection with their restaurant businesses.''

Ms. Florendo says that when she signed the settlement ''I was emotionally distraught, my work was affected. People wished me luck, but the end of this is the law. Who can support me, support all these court appearances?''

Sony Corp.'s New York attorney, Ned W. Branthover said, ''We think it's a fair and reasonable settlement. I was under the impression she agreed to it because she thought it was fair and reasonable.''

Ms. Florendo says she lacked the money to fight any further.

''All I was asking was to let my name survive,'' she said.