With family over there, I travel there often during the summer months for some of the festivals that take place annually near them. In all of those trips over the years, I can honestly only recall maybe 3-4 times where the weather was slightly humid…and by "humid" I mean the temp topped out at about 82 degrees and that lasted for a day, possibly two. But then dropped right back down on following days to the low 70s and even the 60s. You need to bring layers to Ireland, no matter what time of year you travel (even July). Along the coast in the dead of summer I have worn jeans with a long sleeve tee and a fleece zip up over the tee and I was still cold when the wind was blowing.
What Irish women in their late 40s wear is totally dependent on what they are doing - but it's pretty close to what North American women wear. Casual/Daytime: jeans, tees, jackets, scarves (light cotton or silk ones in the summer, wool & cashmere in the winter), skirts, capri pants, yoga pants, hoodies, sneakers, ballet flats. Dressy/Nighttime: Nightclubs, fancy restaurants, etc. - dresses (from maxi to mini), jackets, jeans (generally of the darker rinse and slimmer cut), trendy tops, more scarves, strappy sandals or heels.
Yes, most hotels will provide a blow dryer (if not wall-mounted, the front desk generally has one down in the lobby if you ask) and toiletries will vary - some are just soap & shampoo. Others will have lotion, conditioner, mouthwash, etc. I've been to some very small B&Bs where it was just a bar of soap.
Designer goods - would help to know exactly what you are looking for… clothes? handbags? jewelry? shoes? hats? Big name chain stores - or small boutiques with bespoke offerings? Dublin, being the largest city, will have a wide variety - but plenty of good shopping in other cities like Galway, Cork, Belfast...