Hello,
I understand your concern.
There are many reasons that could be behind 
shortness of breath.Cardiac & Respiratory problems are usally common behind it.
Since you have already undergone 
Blood test,EKG,Blood Pressure check up,and they are normal.It could be even simple 
anxiety behind her breathing problems.I would advise her to relax,go for 
yoga,do activities to get relief from 
stress.If she feel better with this,it is just anxiety.
If she doesn't feel any better with this,you should go to pulmonologist for further investigation like chest X-ray to rule out the problem.
Wish your wife a rapid recovery & health life!
Thank you for choosing us with your problems.  
Let us know if any further queries.
Thanks for choosing healthCareMagic!
With Regards,
Dr.Viraj Ravin Shah