When my missus first told me about the negativity, I thought it was in her head.
After a few weeks I went along to the gym and kept away from her and did my own thing but watched as she worked out. It was the 20-something bro's just milling around and chatting that seemed to have the issue. They'd just stand and watch, make comments, laugh when she struggled a little, just generally being idiots.
I noticed most of the older experienced members who were solo working out to be the most friendly towards her, offering her spots in some occasions. Ulterior motives maybe
Worth pointing out she's a Virgin Active member, of all the gyms i've been to, this chain attracts the biggest idiots.