My wife has some mobility issues as well and when we decided to get our HDT I looked into step alternatives. It turned out that she can access the truck, with a little help from me, without any modifications, but I was looking at these options, maybe one of these can work for your wife.
Several people have used this modified option https://photos.app.goo.gl/e2sc8BSgoS8kddkM9
These are foldaway steps and ladders.
Safety step ladder with fold away top rail (use or don't use) https://www.littlegiantladder.com/products/safety-step-ladder
Brophy Camper Scissor Steps - 4 Steps - Aluminum - Non-Slip Tread - 24" Wide - 300 lbs https://www.etrailer.com/RV-and-Camper-Steps/Brophy/AS24.html
Cotterman StockNStore folding rolling ladder https://www.grainger.com/product/COTTERMAN-3-Step-Folding-Rolling-Ladder-46C347
Cotterman folding latter catalog pages PDF http://www.cotterman.com/wp-content/uploads/2017/05/SNS-103.pdf
Step and store 3 step ladder https://www.uline.com/BL_1439/Step-And-Store-Ladders
Vestil 3 Step Rolling Ladder With Wheels https://www.walmart.com/ip/Vestil-3-Step-Rolling-Ladder-With-Wheels/120202671?action=product_interest&action_type=title&beacon_version=1.0.2&bucket_id=irsbucketdefault&client_guid=7a9fad1e-bec8-43ad-3a01-f62672f3dd03&config_id=2&customer_id_enc&findingMethod=p13n&guid=7a9fad1e-bec8-43ad-3a01-f62672f3dd03&item_id=120202671&parent_anchor_item_id=189940578&parent_item_id=189940578&placement_id=irs-2-m2&reporter=recommendations&source=new_site&strategy=SMT&visitor_id=YCJECgnbSfBON8l_wp9BMQ
TorkLift International - Glow steps http://www.torklift.com/index.php/products/steps-handrails/glowstep
I hope this gives you some ideas.
Roger