1. Under the assumption the mane six are in their twenties Mrs. Rarity's mom does not look seventy (I'd guess mid-late forties) 2. Aside from being on the pudgy side and her hair starting to grey, Mrs. Rarity's mom don't look that much different then Rarity 3. Spike you're going to live to be thousands of years old, get use to those around you ageing.

Oh dear I seemed to have misread that, my apology.

However my other two points are still valid.