The vagifem is a tiny amount of oestrogen, delivered to skin tissues where it is needed.
The vaginal, vulval and urethral areas have receptors that bind with the oestrogen and this keeps them healthy and functioning. When there is little oestrogen available, they will gradually decline. Hence the old term 'vaginal atrophy'. As this happens, the skin becomes more vulnerable to damage, functions less well, and is vulnerable to infection. Hence new term 'Genitourinary symptoms of menopause' The skin in the urethra has receptors too, as it comes from the same tissue when it is first formed.
Regular external oestrogen helps, along with good care - keep away from irritants - wash with water or something like Dermol. Keep moisturised (I use the demol, but there are vaginal moisturisers like Yes etc available) use a lubricant (like yes or sylk - one that does not contain irritants)
Also, drinking plenty of water during the day helps a lot with bladder irritation.