Socket 1155 is fine, especially for what your mom wants to use it for. If I can only pick from the options above I would say 2 is the best. 1 is going to be more expensive. I honestly haven't tried buying used PC parts so I can't really offer any advice since I have no 1st hand experience with it.
Also you could upgrade the ram to 1x8GB or 2x4GB of RAM. Its nice to have and I can't imagine going back to 4GB of RAM.
So something like this: http://pcpartpicker.com/p/XKd4YJ or this: http://pcpartpicker.com/p/ZRVTmG
You could also go for something lower end than a r7 260x, it was just the first thing that came to mind
Selling the GTX 550 Ti was a mistake since it fits your gaming needs the best right now (I hate it when that happens). Anyways, I definitely agree with nahl that upgrading to 8gbs of RAM would be very beneficial to the system. Your best off keeping the LGA 1155 motherboard for budgets sake and upgrading the cpu. What is your budget?
Well I wanted to sell it to my friend but he hasnt gotten from me yet so I can just tell him I am reconsidering not selling it.
I am considering(if i get a good deal on a graphics card better than my HD 7850 on my main rig) transferring to this family pc which I know will be overkill for it. I really want to stay around the $200 mark and to be honest i think 4 gb of ram is fine on this system so just a CPU + GPU upgrade would be nice for that mark
A Intel Pentium G2030 or G2120 will run ya around $30-$50, I've bought a few used on eBay for about $40 with shipping. Far as video cards go a 260x or GTX750 (non-ti) should be available for $100 or less. This will serve your gaming needs. Neither of the cards above will out perform your hd7850.