Honestly, be honest and just tell her the way you feel, try find your own words for it and if you're anxious/ nervous try writing a letter you could give to her :D
(but i wouldn't tell her over text, it's never a good idea lowkey 😭 )
since you don't see her that often, the next time you do meet, you could have something prepared by then :D maybe do something nice together to take the edge off
(this is just a suggestion tho, in the end it's your decision how you go about this)