There’s honestly no harm getting the recommendation letter that you want. If it’s a good letter you can use it. But if it’s not, it is a pity but it won’t actually affect you at the end of the day. In my opinion, having that working experience on your CV is going to be far more important than a letter. Regardless I think you can still ask. Perhaps if you superior is unfamiliar with you, you could prepare a list of your achievements during the internship to show the progress you’ve made, and ask if they would be open to leaving some nice words for you. Keep in mind that you’re asking for a favor, so even if they reject your request, don’t take it to heart. Be appreciative but not pushy.