Is it bad if she doesn't smile much on a first date?

Resting expressions vary a lot. Some people look stern in photos and in person, especially when they're concentrating or a bit anxious. The useful question is whether she is participating. Look for whether she answers with more than a word, whether she asks you something back without prompting, whether she mentions a detail you said earlier, and whether her body turns toward you over the evening. If those are there, a lack of smiling is probably just her style or nerves. If she gives one-word answers, keeps her coat on, and steers toward leaving, that's a clearer signal, and you can take it seriously without needing her face to confirm it.

Your follow-up should give her an easy way to show interest without asking her to rate the date. A short, warm message that references something specific from the night works well, and a plan that's simple to say yes to works better than a vague "we should do this again sometime." Don't use the text to fish for compliments or to ask whether she had fun. If she was warming up during the date, a relaxed text will let that continue. If she wasn't, a relaxed text lets her decline without awkwardness, and you get an answer without pushing for one.

Send your follow-up the same day or the next morning, not late at night and not after a long gap that makes it look like you were deciding. If she replies warmly, match her pace and pick a plan. If she replies briefly but politely, that's a fair answer to a first date, so accept it and don't send a second text trying to rescue it. If you get no reply after one message, leave it for a few days, then let it go. Sending a second or third message to a non-responder reads as pressure, and it ends any chance of a second date you might otherwise have had.