Things that tend to help with separation anxieyt are a combinations of things. One is to take your dog for a nice long walk before you leave, preferably 30 minutes or long. Make it a long, quick paced walk to tire your girl out. This is best for those days that you are going to be gone for a long time.
Second is to use a low-key approach to leaving the house. Ignore your dog before you leave and after you come home for at least 5 minutes or more. If your house is hectic with everyone running around getting ready to leave, this can put the dog in an excited mood and then suddenly she is alone. If this is the case, put her away from everyone, say in a bathroom until the frenzy is over.
Don't punish or shout at your dog when you come home and find she’s scratched the door or carpet, destroyed something or whined. When you do, you increase her stress level rather than reduce it. I do recommend the decorative sheet metal on the bottom section of doors that a dog is destroying. They effectively stop the destruction and often the scratching of the door itself since the dog doesn't like the feel on the nails. This is if she is destroying doors. Often owners complain of this.
You can provide her with small stimulating toys or toys that you can fill with treats. The kong is a popular one and you can fill it with peanut butter or yogurt and freeze it. Give it only when you are leaving for long periods of time to keep her busy. If she is holding the kong and licking it, she won't be whining or destroy something else.
Sometimes leaving a TV or radio on can help a dog with this problem as well. Also remember to not reward a dog's excitement to you with petting and affection or even eye contact. You want to show her nice calm praise when she is being calm. You can tape noises of you in the shower or in a room where she isn't allowed and play that on a loop when you are gone. It can help.
The best way is to crate her. This prevents injury to the house and protects her as well. The best way to get a dog used to a crate is to get a large one and start feeding her in the crate. Don't lock the door or even close it. Just put the food bowl in there and let her go in to eat. After a month or so, start shutting the door behind her when she goes in to eat and open it as soon as she is finished so she gets used to the door being closed and opened. After a little while, she won't think of the crate as a bad place. I think we can solve it without the crate, but still it is a good idea for a dog to be able to be crated when necessary.
.Practice leaving the house, opening the door immediately and rewarding her with a hot dog treat if she did not scratch, bite and carry one. This teaches her that you leave but come back quickly. Once she seems to not do anything when you initially leave, lengthen the time she must be quiet for you to come back in. Change the time as well. Make it 2 minutes one time and 10 mintues another, so she never knows if you are gone for an hour or gone for 2 minutes. It helps her stay calm for longer periods of time, just be sure you reward her when she is good. Start by just staying outside the door so she knows you are there. Then move off a bit and come back. Eventually you will need to even get in your vehicle and move off and come right back.
Another thing is to remove the triggers that your dog uses to realize that you are leaving. For instance, if you always pick up your keys before leaving, start picking them up and walking around the house with them. Or put on you coat and wear it around the house, so the dog no longer knows just by your actions that you are leaving soon. Also carry around your pocket book or leave without these things. Remember when training to be sure to have your keys or other things that you would have on you when you leave or else the dog will know you are only gone for a minute. I had a dog that would whine when I picked up my purse but not if I just walked out the door. She knew if I didn't pick up the purse that I would be back in just a few minutes. Dogs do recognize patterns.
These should help her separation anxiety and boredom and help curb her whining.. It will not be an overnight cure and will take work on your and your family’s part to be consistent in your interaction with her. Here is a site that also offers idea to combat separation anxiety.
If she misses her companion, that might be something to consider as well, though that may double your problems since the young dog might learn the behavior from the current dog.