Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that Lucy isn't passing stools as she normally does and I understand your concern.
Olive oil is a digestible oil and so may be less effective at easing constipation. By the time it gets to the colon where hard, dry stools make passing stools difficult most of it is no longer in the gastrointestinal tract. You are better off using the nondigestible lubricant products like those for cats with hairballs, such as Laxatone.
Pumpkin is great for increasing fiber, which stimulates colonic motions, and softening stools making them easier to pass.
That said I'm not sure that she is necessarily constipated if her last stools were softer yet she still isn't passing them.
Her scooting tells me the primary trouble may be full or infected/impacted anal glands that are either very uncomfortable to pass stool by or are not allowing stools to pass normally.
If the glands are unable to empty eventually with nowhere else to go the glands become very full and uncomfortable and thus the pup will scoot in an attempt to relieve the discomfort. This is a common problem for dogs and seems to be more common in overweight dogs that are fed lots of table scraps or eat a diet low in fiber. These glands are normally expressed when passing stool but if she routinely eats a diet low in fiber her stools may be too small or infrequent to empty them.
Dogs will scoot their bottom on the ground, even sometimes spinning in an attempt to empty their glands, or they may lick their bottom excessively.
As far as long term prevention if this becomes a recurrent problem for her I recommend weight loss if she is overweight.
I also recommend decreasing or stopping entirely table scraps.
A diet higher in fiber, such as a weight loss diet or mature diet, may help. Sometimes a prescription food very high in fiber like Hills r/d or Purina Veterinary Diets OM is needed.
If she will let you touch the area she would benefit from a cool compress to the perianal area, patting dry and then applying a light coat of cortisone cream (like cortaid) to the area a couple times today and until you can have her anal glands checked.
Unfortunately the more she licks and scoots the more painful the area will be and the more tissue trauma she will cause. If the area appears red and she is licking then an e-collar (lampshade) is a great idea until she can see a veterinarian.
I know that she is uncomfortable but if she is still eating and drinking normally today then this isn't an emergency, but I would call her veterinarian to try to get an appointment today to check her anal glands.
Ideally I recommend that you do not feed her breakfast the day you take her in as they may need to sedate her to treat her. But if you've already fed her just don't feed her any more today until she is seen.
There are other reasons for perianal itchiness, such as a flea infestation, tapeworm infections or a food allergy reaction but the most common cause is anal gland troubles.
Best of luck with Lucy, please let me know if you have any further questions.