I'm thinking of isolating my significant other from her friends
Why do you think that isolating her is the way to go?
Not sure if I am ready for taking this step, maybe later
So you haven't done it yet but are thinking about doing it. This isn't right, people deserve to spend time with who they want too.
I know that but I'm worried she might be too close to them and she might forget about me in the long run.
I think that that might be an insecurity that you need to work on within yourself. There is no reason why you should be controlling who she does and does not have contact with.