I'm 5' 4" tall and have an inseam of 710mm. My small frame / 26" tire Giant Sedona has a stand over height the same as my inseam and its OK. I would not buy a bike with a standover height less then my inseam. So you will probably be fine with that bike. But try it out anyway first if you can.

In fact my next bike will be one of those low entry / girls bike. At 69 I tried my cousins comfort bike and love it. It's 27.5" x 2" tires are good for pretty much any terrain.

veganbikes is right on about a bigger bike feeling more stable. When I switched bikes from my 26" comfort bike to Bills 27.5" low entry, it was a more relaxed ride, Which for a comfort bike might be a good thing. Switching back to my bike was a real surprise. After riding his bike for a while, My bike felt so twitchy it took several minutes to get used to it again, especially at low speeds, but when I did, its just fine too.