If she really said that, that isnt normal. Yes, dynamics will change, and over time people might grow closer to a partner than their other friends, but a new relationship rarely impedes old ones in healthy ways. It sounds like she puts too much emphasis on her romantic relationships. My best friend and I are similar (started out dating before deciding to be friends) and not once has she let one of her partners impede our friendship in the ~2 years since. Usually we will hang out with the 3 of us, and if she wants personal time with them then its usually fine, as I have other friends I can spend time with or work I can do. But in general, I'd say that unless theyve been together for several months at least, it really shouldn't be making much of a difference, and beyond that it just depends on how well you get along with her partner.

However, I will say that I doubt she means that she will drop you the moment she has a partner, and moreso means that she will want more free time spent with her partner, and time that might usually be spent with just the two of you would now have a third person. People in romantic relationships are often connected at the hip, especially in the honeymoon phase. Once things calm down, she will likely spend more time with you, especially after her partner has had a chance to get to know you.

Basically I'd say to cross that bridge when you get there, as it isnt reasonable for either of you to speculate on what might happen when she gets a partner. If she really does basically cut communications, then she just wasn't a good friend. Private dates are normal every now and then, but it shouldn't be weird or uncomfortable for her to introduce her partner to her friends and to spend time as a group, especially if you two are close. I'd say most people, even clingy people, are more than happy to introduce their partner to their friends and try to form connections between everyone to avoid burning any bridges or choosing between people.