DEAR ABBY: I never thought I would have to write a letter like this, but I need someone to help me, and I thought of you.

One of my daughters and her husband borrowed $7,000 from me almost five years ago. They promised to pay me back within a year, but so far I haven't seen a dime of it.This daughter and her husband both have good jobs and seem to have money for everything else. I am 77 years old, live in a senior citizens apartment house and am doing without a lot of things I need.

I am sorry to say that I don't have any proof that I loaned them the money. I guess I should have asked them to sign a note for it, but I didn't think it was necessary.

Now what should I do? - TRUSTING MOTHER

DEAR TRUSTING: Without written evidence showing that your daughter and her husband borrowed $7,000, it will be very difficult to collect. You might try the following, suggested by a reader in an earlier column, as a solution to an identical problem:

An elderly couple had loaned their son $5,000. He promised to repay it in 90 days. They foolishly had nothing in writing. Four years passed, and not a cent did they receive, so his mother wrote him a letter asking if he could please make even a partial payment on the $7,500 he had borrowed.

Quick as a flash he wrote to say that he did not owe them $7,500 - it was only $5,000. Mission accomplished! They got it in writing.

DEAR ABBY: You frequently remind your readers to make sure their children are "buckled up" in seat belts when they get into a car. But no one mentions the fact that pets can just as easily be thrown from a vehicle and injured.

It makes me sick to see a dog loose in the back of a pickup truck or hanging out of a car window. All it would take is one quick stop or a sharp curve to send that animal flying into the street.

My dog loves to go for rides with me. He sits in the passenger seat and I buckle the seat belt around him. For smaller pets, there are carriers one can attach to the seat to provide safety for one's pet. I hope you feel this is important enough to put in your column. - LIZ IN CALIFORNIA

DEAR LIZ: It is. So, dear readers, listen to Liz. And if you're lucky enough to own a pet who adores you, the next time that dog or cat follows closely on your heels when you head for the car, remember: Pets rely on their owners to protect them, so don't let yours down. Inquire at your local pet shop about car seats for pets.

CONFIDENTIAL TO M.C.D. IN SCOTTSDALE, ARIZ.: Whether she nags because he drinks or he drinks because she nags is not the issue. Nagging irritates only the giver. Drinking irritates the liver.

Everything you'll need to know about planning a wedding can be found in Abby's booklet, "How to Have a Lovely Wedding." To order, send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada), to: Dear Abby, Wedding Booklet, P.O. Box 447, Mount Morris, IL 61054. (Postage is included.)