Sounds pretty good, but I have a couple of suggestions that should make it more fun for your daughter, and a nicer trip for all.
First, do not spend any nights in Milan. It is a big, busy city, and can be very hot. There is no scenery there, nor swimming, and “cute shops” are not Milan’s strong suit—-it’s high end fashion and design that are important.
Second, if she does not like to hike, you don’t need so much time at Wengen. There is one irresistible hike there that she cannot help but enjoy; the Panorama trail from Männlichen (a cablecar ride above Wengen) to Kleines Scheidegg. The scenery is gorgeous and the trail is easy. She might even like some of the offerings at the playground up there—-my 11-year-old grandsons, and their father, had fun there on the slack line, and climbing in and out of the huge cow. There more adults playing there than kids when we went.
https://www.maennlichen.ch/en/summer/experiences/alpine-herdsmans-playground.html
From Kleine Scheidegg, you could ride the train back down to Wengen (don’t walk, especially on a hot day). Or you could walk up to Eigergletscher and ride the gondola down to Grindelwald, walk around the village, and return to Wengen by train.
Then figure out what else you want to do from Wengen, but I will suggest you only need 3 nights there, and you can head to Luzern for 3 more.
But do not stay in Luzern—-it is crowded with tourists and we have not found a hotel to our liking there. Instead, board the lake boat and ride 40 minutes to the lakeside village of Weggis. Book 3 nights at the Seehotel Gotthard, right on the lake. Your daughter can swim in the lake or in the outdoor pool with a view right next door (hotel guests have access to that pool).
https://www.gotthard-weggis.ch/en/
We were there last September with our family and everyone, especially the 11-year-old twins, loved it. They had the 3d floor family room in the turret (the one on the right in the photo and felt like princes.
With 2 full days at Weggis, you can use one to explore Luzern (accessible by boat or bus/train). Use the other to ride the cablecar from Weggis up Rigi to Rigi Kaltbad, and tempt your daughter into another hike, with beautiful views over the lake to the peaks opposite. Continue by cogwheel to the summit ar Rigi Kulm if you like. There are easy and very scenic hiking trail up on Rigi, and a mini-golf course at Rigi Kaltbad if she likes that. Or maybe you and she would like some mother-daughter spa time in the outdoor infinity pool you can see in these photos:
https://en.hotelrigikaltbad.ch/wellness-spa
You need not be a hotel guest; you can pay for entrance to the spa, and children are welcome in the indoor and outdoor pools.
for more water activities in or near Weggis, see here:
https://www.rigi.ch/en/experience/at-the-lake/swim-vacation/water-activities
The Pedalo, motorboat, and SUP rentals are at Küssnacht am Rigi, a 10-minute bus ride from Weggis. Also, the Seehotel Gotthard has a couple of sea kayaks available to guests for free.
After 3 nights at Weggis, you take the scenic Treno Gottardo over the mountains toward Locarno, but you leave the train at Bellinzona and transfer to one heading to Milan. Stop on Lake Como, and overnight by the lake instead of in Milan. The train ride into Milan the day of your flight from Como is 40 minutes, leaving you plenty of time to get to the airport for your evening flight. If you prefer, you could stay on the Treno Gottardo to Locarno and overnight there, a 2-hour train ride from Milan.
You can catch the Treno Gottardo from Weggis by (a) taking the boat back to Luzern and boarding there, or (b) taking the boat from Weggis south down the lake to Flüelen and meeting the train there. We did that and all were very happy with the boat ride—beautiful and relaxing.
So, 4 nights Stresa, # nights each in Wengen and Weggis, one at Como (or Locarno). None in Milan.
