Photoshop to purchase is about $700 US, although you can rent per month. You can do almost anything with it, but the learning curve is steep. But this may be overkill. You might be satisfied with Photoshop Elements, which is less than $100.
I suggest you take the free 30 day trial and see if PSE fits her needs.
Thanks Curt, we will take your advice and see if Elements does what she needs.
I'm inclined to agree with Curt. Elements has all the features you'd need to that job. Scott Kelby describes PSE as '90% of Photoshop and 10% of the price' It's a job to argue with that.