Can I assume that your mum is mortgage free and those buying from her are not?
If course they will turn the screw in the financial environment we are currently in. If mortgage offers expire and they have to add 0.5% to their rate, coupled with the crippling anxiety of a falling market, folks will panic.
Perhaps you and your mum need to adjust their expectations. We viewed 5 houses in April and May owned by people who were older than 65. One couple had already moved out. Two couples said they would move into caravans they already owned in order to facilitate a quick and successful sale. These people appear to have taken good advice from EAs: if you want a quick sale from FTBs in a falling market, bite their hand off and bend over backwards to make that happen before they have the time to change their minds. The longer a purchase takes, the greater chance there is of cold feet happening.
With respect to the offer and the sellers being on the fence, perhaps they are worried about their own affordability or job security with a recession looming.
I think your mum needs to do a round of interviewing EAs and she needs to pick one with the best sales strategy, which doesn't involve putting it on the market at current market rate, bunging it on Rightmove and hoping for the best.
And, as tough as this is for you, you need to take a reality check. This is the market we are in and a vast number of sales are falling through. 1 in 6 houses in May accepted 10% under the asking price, so ask yourself if EAs are overpricing to get your mum's business. A more realistic strategy would be to go on at significantly under and hope it generates a mass of interest which will see her eventually getting the asking price she needs.
Does the house need work doing to it? Rewiring, kitchens, bathrooms, carpets, landscaping? Hopefully those will have been priced into any asking price, because almost nobody wants to take those on at the moment because they are horrifically expensive.