Is her goal to make money? Or is it just an outing and a chance to socialise with people who share an interest? If the latter, then she may be getting everything she wants out of the experience so doesn’t see the need to change anything, in fact being more popular might be bad in that context. (Edit: just realised this is pretty much what one of the other replies asked, apologies.)

Otherwise, and I’m no expert at this stuff by any stretch, but purely from a casual attendee’s perspective, location is really important. Don’t be in a corner where there’s hardly any foot traffic, and if you can, try to set up next to whatever booths are busiest at your events - for the ones near me that’d be things like coffee, ice cream, bakery etc depending on time of year. They are always packed, and food/drink booths usually have people with a few minutes to kill while they’re waiting for their order.

If you have dozens of people milling about in front of your stall waiting for a coffee, the odds of someone spotting one of your products increases massively, and some of those may turn into sales.