dog that suddenly started to carry around a toy dog and whining a lot as if it were her baby

Question
We have a female Chiweenie dog, age 18 months, who has had a small toy shaped like a dog for awhile and never played with it much.  Then all of a sudden ( 5 days ago ) she is carrying it around as if it were her puppy and won't leave it alone, except to go outside to potty and then is whining a LOT when she is away from it any and even has been picking it up ( quite carefully as if it were a puppy ) and sometimes carries it around almost frantically going from one place to another and whining as she does this.  She won't get away from it and when she does go outside or can't see it, she dashes back to pick it up.  She also sleeps with it 'cradled' against her after first turning around it 5 - 8 times trying to get it just right when she lays down.  We think she about to go into heat and some have said we should have her bred for at least one liter as it seems like a severe mothering need she is displaying, but we are worried if she does have some babies, she may be even worse when it comes time to let them go.  Any advice for us, please, would be greatly appreciated.

Answer
First, you need to consult your vet as this may be as much a medical problem as a behavior problem.

Next, take pity and have her spayed. I can't predict how she'll be after a litter, but a mothering instinct doesn't go away after a litter. The only way to make it go away is to remove the hormone producing organs that are the source of it. I will never recommend breeding a dog. It's unfair to the dog and it's unfair to the millions of homeless dogs in this world. A dog in heat is an unhappy dog and small dogs sometimes don't survive breeding. Be kind.