There are a couple things to consider in your case. For us manual dosing pool owners who may leave the home for a few days, you increase your FC to SLAM level. That should buy you a couple days or so depending on the heat/sunlight while you're away. You can also use your in-line chlorinator or floater with a couple tabs for a few days. When you get back, pull them out.
Something else you might consider is your current CYA (40). While that is smack-dab in the middle of the TFP recommended CYA range, TFP also recognizes that some location around the country have intense heat/sunlight. Not sure what part of TX you're in since the location doesn't show under your profile name, but here around San Antonio, our temps are about to shoot-up. My pool gets full sun from dawn to dusk. My CYA is at about 50 right now. I will increase it to 60-70 between May-Sept just to preserve FC from that brutal South Texas sun. In doing that, I increase my FC level according to the Chlorine/CYA Chart, and my pool is able to hold FC better in the summer to keep me in that 2-4 ppm expenditure range. So you might consider increasing CYA as well as summer approaches if your pool gets full hot Texas sun.
Every pool is different, so it's something you have to try. With the right test kit, you have the tools to evaluate what works best for you and your pool and adjust accordingly. That's one of the greatest things about at-home TFP care.
PS ~ I use HEB's Bravo bleach, but sometimes grab Wal-Mart's Great Value. They're rated at 8.25%, so you might get a little more kick/results from those. My pool is slightly larger than yours, and I only need to add 1/2 gallon of bleach each day (2.5 ppm) for me.
How long to clean it up? Every pool is different. Some SLAMs take a few days to a week. Really green pools can take 2 weeks or more. Your sister's pool sounds like one of the latter. But a lot of that time boils-down to the consistency applied by the home owner in testing, increasing the FC when it fall below the SLAM level, removing bulk trash, sweeping/brushing, and cleaning the filter. Those things are key. Of course once the pool begins to clear, owner's have to be vigilant to look everywhere in the pool for any potential algae hiding places (behinds lights, in/under ladders & steps, etc). As you know, it's very important to be consistent across the entire SLAM progress.