I have a highly playful small puppy (morkie) a little over a year and we want to get her another doggy friend while my parents work all day and I’m gone in university… Would getting another small dog that’s a senior be okay or could my dog hurt it?

You just need to make sure they meet before committing. If anything, a senior dog would have more issues with a young dog and be the one to potentially harm the pup. But a meet and greet with both dogs will let you know right away how much they can tolerate.