What are the next steps I (25F) can take in this "relationship" with the person (25F) I'm seeing?

TLDR: I (25F) have met once with and texted a woman (25F) who seems a bit avoidant and shy. I always find myself initiating texts and plans. We were supposed to go out for a concert, but she got sick and canceled it, especially without rescheduling or asking about new plans. I feel bad because I keep texting her, and while she's mainly reactive to my texts, she takes forever. I last texted her Wednesday, and she hasn't responded yet (it's Saturday). Is this relationship worth it, also I haven't told her my feelings towards her.

Backstory:

My (25F) friend invited me to her graduation party in mid-August, and one of her relatives was there, we'll call her Diana (25F). I was the only person who was not related to her who was invited to my friend's party. I interacted with Diana a little bit. At this graduation party, I found out Diana is bi, mainly because she was outed by her aunt. Anyways, I felt a certain way about Diana, and I found her social media, reached out to her there, asked her out for coffee/initiated planning the meetup, and got her number. We actually met up in late August, the meetup was 2 hours from both of us (we live 4 hours away). We had an 8 hour date (?), where we had food, walked around, and talked. I even came out to her. On this meetup, I learned/noticed that Diana 1) talks extremely quietly, even when we're walking around or eating 2) avoids eye contact 3) does not express emotions/has a "flat affect" (e.g. when she finds something funny, she hides her laughs) 4) has to be set up to date by her friends and 5) does not use her phone much. Also, while waiting for the food at the restaurants, she would bring out her diary/journal and would write in it, or read her book. This happened 3 times. Also, after she learned about my sexuality, she started talking to me more and asking me more personal questions.

So Diana is in a graduate program that involves a lot of reading and writing, and from my understanding, is working several jobs as well. Before we went out for coffee, she had finished her 2nd week of school. Since going out for coffee, I would text her, and she'd eventually started taking a while to respond. I kind of attributed this to maybe her feeling tired from her responsibilities. I was okay with the slower texts, as long she was texting me, answering my questions, and inquiring about me. Well, I ask her if she wants to do something together again, and I take the reins on planning. We decide to go to a classical music concert, in early October, and we each pay $90 for tickets. Basically, I also ask about if she wanted to do other things apart from the concert, and I make plans based on whatever she says we can do.

So anyways, the concert date is approaching. Our texts are pretty slow and spaced out, but she brings up the concert and that she's excited for it. The day before the concert, though, I let her know about parking and other logistics planning stuff, and she's agreeing. I think everything is going fine, until she agrees to plans and then immediately says she's not feeling well (she had to leave work early) and that she may not be able to go to the concert. I'm a bit sad, but I decide to check-in on her the morning of the concert, and ultimately, she tells me she's not going to the concert because of how sick she feels, and that she wants me to enjoy the concert without her. I actually don't end up going, and the next day I get a text from her asking about the concert. I tell her very honestly I didn't go because I felt sad, and she apologizes. I divert the conversation to school, and she tells me she's struggling with school.

Now, the last time we've texted was Wednesday night. It's Saturday and I'm still waiting for her text. I haven't told her how I feel about her (I really like her), and the last conversation was sort of about school. I hope things aren't over between us, but what are the next steps I could take? I hope this is not over.