If you're choosing a magnifying glass for your grandma, ease of use and comfort are usually more important than maximum magnification. Here are the main things to consider:

Choose moderate magnification first.
For reading books, newspapers, medicine labels, recipes, or mail, around 2×–3× magnification is often a practical starting point. Very high magnification can produce a smaller viewing area and make it harder to keep the image in focus.
Consider the lens size.
A larger lens is generally better for reading because it covers more words at once. A small, high-power lens may be useful for examining tiny objects but can be frustrating for continuous reading.
Look for comfortable handling.
If she has limited hand strength, choose a lightweight model with a large, comfortable handle. For extended reading, a hands-free or stand-mounted magnifier may be more convenient than one that must be held continuously.
Consider lighting.
An LED-lit magnifying glass can be particularly helpful for reading in dim rooms or examining small print. Look for simple controls that are easy to switch on and off.
Think about what she actually wants to see.
Books/newspapers: large lens, about 2×–3×
Small labels or medication packaging: 2.5×–4×
Needlework/crafts: moderate to higher magnification
Coins, jewelry, or tiny details: higher magnification with a smaller lens
Frequent reading: hands-free or stand magnifier
Check the viewing area and working distance.
Higher magnification usually means a shorter working distance and narrower field of view. For an elderly person who simply wants comfortable reading, a moderate-power lens with a broad viewing area is often easier than an extremely powerful lens.
Prioritize simplicity.
Avoid unnecessary features if she prefers straightforward products. A lightweight magnifier with a clear lens and easy lighting control may be more useful than a complicated electronic magnifier.

My general recommendation: for a grandma who mainly wants to read books, newspapers, cards, and labels, start with a large 2×–3× magnifying glass with built-in LED lighting and a comfortable lightweight handle. If she needs it for long reading sessions, consider a hands-free/stand model instead.

If you tell me what your grandma mainly wants to use it for (reading, crafts, medicine labels, travel, etc.) and whether she prefers handheld or hands-free, I can narrow down the most suitable type in SISCO Magnifying Glasses.