HELP writing a letter for a book?

[barbie]

so I'm doing a photo book for my mother in law as a Xmas gift and in the book i put pictures of her love ones and on the last page i was thinking of writing something nice for her but i cant come up with anything =/ .. i need help i want something that is thoughtful not so short tho .. something that will say how a wonderful mother aunt sister / person she is ...