Her laissez faire attitude towards contraception may indicate that she is slightly immature. It’s probably not a major deal in the long run, however. People usually mature quite quickly in their early 20s. Set clear boundaries with regard to contraception and if she’s fine with that, then you probably don’t have anything to worry about.

In regard to her saying she loves you, it is very likely that she sincerely feels that way. Love is unpredictable. Very often, it hits you without prior warning. For some people, it takes time for them to feel that way. For others, it can hit them early on in a relationship. I get it though. Having someone who is overly keen, especially if you sometimes struggle with unconscious detachment, can be slightly unsettling. If I were you, I’d count your lucky stars that you’ve found someone who is emotionally available. Being with someone who is overly cynical and/or emotionally closed-off is a real nightmare.

While the general gist of my advice is that you should try not to overthink these things you have taken issue with, and continue putting effort into your new relationship, you still need to remain observant for potential red flags.