Hi Meta, Welcome.
I get a little uneasy when my Ts take vacation/I miss session with them because I'm very habitual. When I don't see my T's I have a hole in my week, I miss them and feel a little lost without them. When my T told me recently she was going on vacation I was happy for her, and also said I'd miss her. It's not uncommon for clients to get angry, feel abandoned, feel helpless, feel like they don't care, go back and fourth between 1000 things to feel - all of it is okay! And not feeling much, or just hoping she has a good time is perfect, too. It's your process. Not all attachment stuff is intense and it could depend on where you are 'in it' at any one time - you may not feel this same way (or you may) 2 months from now, 2 years from now, etc.
You're not doing anything wrong, your process is yours. I used to feel a LOT when I first started posting here that there was something inherently wrong with me for not having an attachment in the same way as others. Sometimes I still feel backward/wrong but I have done a lot of attachment work with my T - it's just been slow and I don't know if I'll go through the same stuff as other people have and it may be the same for you. There is no one way to do therapy (I've told myself this 1000x when I feel my attachment stuff doesn't fit in).
But anyway... just be open to what happens
You're okay and how you feel is okay. You can do good attachment work with your T AND be okay with her going on vacation.