You can buy a 64 GB SSD and a stick of RAM for around $100
If you want to go that route, that's your perogative. I'd recommend checking her existing storage situation to make sure 64GB will be enough to hold everything she needs. I'd personally never buy an SSD less than 90GB. (120GB is better) Keep in mind, that if you're going to be buying another super low cost laptop as a replacement in the next couple years, it probably won't have an SSD, so you can transfer this SSD into the new laptop.
If I were you in this situation, I would buy the SSD first, install it, and see how the situation improves. If it's still slow, then get more RAM. Kingston V300 120GB
for $80 (cheap 120GB)Samsung 840 EVO 120GB
for $105. (better choice)
Main: i5-3570K, ASRock Z77 Pro4-M, MSI RX480 8G, 500GB Crucial BX100, 2 TB Samsung EcoGreen F4, 16GB 1600MHz G.Skill @1.25V, EVGA 550-G2, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Crosley D-25 Case Mod