Please, check the FAQ: Tips for writing R-related questions and FAQ: What's a reproducible example (`reprex`) and how do I do one? to help us help you.
What 
did you use to get the tweet ? What is your code ? What have you tried ?
Also have you check in R code outside the Rstudio viewer what is inside your data.frame ? It is possible that the viewer is cutting string for better readibility. Something like:
tweet <- #some get tweets function
tweet$text[1]