>>382602450
They’re not a true friend if the only thing they are looking for is “entertainment” instead ofbuilding loyalty and camradarie with shared experiences. 
If they’re a friend they could’ve invited you too. Or at the very least not mind you joining in on their adventure to the other friend.

In any case there are two types of friends. Friends for fun who are there wanting to enjoy the fleeting life with. And Friends for life who are there to navigate life with and enjoy everychallenges together.
First type is a more fragile fleeting thing. 

Note that there is nothing wrong with both types. Just know what friends you are making and invest time and attention accordingly.