I'm sorry to hear that Ella has a cough and is wheezing and I understand that you are concerned about her.
A cough simply means she is experiencing airway irritation.
A cough can be related to heart disease, including heartworm, lung disease secondary to a viral, bacterial, fungal or parasitic infection or tracheal irritation due to a bacterial, viral or fungal infection.
In a dog that goes to a boarding facility, groomer or dog parks infectious disease is by far the most common cause of respiratory symptoms. Of those kennel cough or infectious tracheobronchitis is one of the most common causes. Because we know that she goes to the dog park often, kennel cough would be high on my list of possible problems.
Even if she has been vaccinated we cannot vaccinate against all of the agents that cause kennel cough and some dogs will still get sick even with the vaccine. The good news is that dogs that are vaccinated usually don't get as sick as dogs that haven't been vaccinated.
As long as she is still able to eat and drinking well, isn't lethargic, isn't running a fever (rectal temperature greater than 103F), and she doesn't have a green or yellow nasal or eye discharge then you can try taking a watch and see approach and using an over the counter cough suppressant.
Make sure she gets plenty of fluids, lots of rest as the more active she is then more she will cough, and eats well. Add warm water or low salt chicken broth to her food to get more fluids in and soothe her throat. The better hydrated she is the better she will feel and the thinner her respiratory secretions will be.
You can take her into the bathroom with you when you take a hot bath or shower so she can breathe the steam which is soothing to her airways and thins mucous, making it easier for her to breathe. You can also use a humidifier in the room she sleeps in,
Her cough and wheezing should slowly resolve over the next 2 to 3 weeks. Most of the time these dogs feel pretty well so it's a matter of keeping them quiet and suppressing the cough if we can.
If the cough is very bad such that she cannot sleep you can use human cough/cold medications with Guaifenesin (an expectorant) and Dextromethorphan (a cough suppressant) only such as Benylin or Robitussin DM can help. Give 1 teaspoon per 20 to 25 pounds every 6 to 8 hours.
If she is running a fever this is almost certainly a contagious infection and if she is running a fever and is lethargic then an examination is definitely warranted as pneumonia may have developed.
Best of luck with your girl, please let me know if you have any further questions.