My friend has started dating,

In the past, I remember feeling somewhat threatened when a friend of mine entered into a new relationship because I feared it would result in us socialising less. Whilst that did end up being the case, I gradually learnt to adjust and accept it, and not allow my feelings to ruin our friendship. 

Although we saw less of each other, we would phone each other fairly regularly.

Sporadic Sparkly said:

I remember feeling somewhat threatened 

I’m guessing that is what is going on for me. I need to work on acceptance. 

Sporadic Sparkly said:

I remember feeling somewhat threatened 

I’m guessing that is what is going on for me. I need to work on acceptance. 

My three main IRL male friends have all married. Two of them are great about regular contact an occasional catch ups (occasional is my pace of life anyway!), the third is very nested since marrying three years ago and seldom makes contact. I hear that that scenario is much more common, leaving the single friend to make one way efforts or fade away into Christmas card territory. So I’m grateful that I’m beating the odds by dint of the particular dynamics of our wee group. 

Speaking from experience, I have found that when female friends are in relationships, they still want to maintain some form of contact with their friends. After all, friends are generally the people who will stick around and help them to pick up the pieces if their relationships don't work out.

Unless your friend suddenly decides to end her friendship with you, which is unlikely if she values the friendship, my advice would be to focus on appreciating the friendship you have, rather than dwelling on how threatened you are currently feeling.