Answer:
She is absolutely correct!
Explanation:
Let the total no. of stickers with Lena be x.
If she sticks 5 stickers per page, the number of pages she will use=

If she sticks 10 stickers per page, the number of pages she will use=

We all know, that the smaller the denominator the larger the number.
Therefore,
Condition being that x is a positive quantity which it automatically is.
So, Lena is right in her reasoning that she will use more no. of pages.