Answered by Shaykh Ilyas Patel
If I visit my sister’s house 50 miles away, am I considered a traveller?
Answer:
In the Name of Allah, Most Merciful and Compassionate
When a person travels 48 miles or more and intends to stay less than 15 days, he is a traveller. In your case, the distance between your house and your sisters is more than 48 miles, hence you will be considered a traveller.
You can shorten all the prayers that come when you are there and whilst traveling back to your home, until you reach home. So it was permissible for you to shorten the Isha prayer as you were still considered a traveller.
Ilyas