Also looks to me like there are benefits to be gained by upgrading to the i5 chip and benefits to be gained by selecting the dedicated video card.
This is true. But..
Without spending the extra $100 or $200 you'd still get a very capable Photoshop laptop. Yes, the performance could be improved, but that's on top of what is already a wholly capable system. There would be no limitation on what she could get done, it would just take a very small amount of extra time to get it done without the upgrades.
A decent laptop mouse would be a big help and the increased productivity (navigating through menus, layers and better control in applying Photoshop effects) could very well let her finish a project faster than with just the better CPU or video card alone.
My recommendation would be stick with the i3 370M and HD Graphics.
Other's thoughts on the same question. http://www.tomshardware.com/forum/291754-33-430m-intel-radeon-5450-upgrade-photoshop