The dryer runs, the clothes come out, and nobody thinks about the vent until the drying takes forever or the laundry room feels warm. Lint that builds up in a dryer vent is a known fire hazard, which is why this is worth doing carefully and comparing before you book anyone.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Know what the vent is
The part you see behind the dryer is only the start. The vent runs from the back of the dryer through a duct to an outside hood. A cleaner might clear the connection at the dryer and call the job done, or might clean the full run to the outside. Those are two different jobs, and they can carry two different quotes. Ask which one they mean before you agree to anything.
Questions that show the real scope
Ask whether they clean the whole duct from the dryer to the outside hood, or only the part they can reach from behind the machine. Ask whether they check and clean the outdoor hood, including the flap, and whether they will tell you if the flap sticks shut or is broken. Ask what tools they use for the duct and whether they clean the dryer's own exhaust path as well. Ask whether they will send photos or a short written note of what they found and what they cleaned. Ask whether they carry liability insurance, and whether they will show you the certificate. Ask whether they are licensed where your city or county requires it.
What to look at in the laundry room
Ask the cleaner to show you the duct length and whether there are turns or a flexible plastic section. Flexible plastic or foil ducting is a sign of where lint likes to hide. Check the dryer manual yourself, since it may say what duct material is acceptable and how long a run is allowed. A good cleaner will tell you if your mother's setup is not up to what the manual describes, and will not pretend it is fine so the job ends faster.
Compare two quotes the same way
Put the two quotes side by side and check each one for what is included, what counts as extra, and what would add to the bill. Extras often include a repaired hood, a replaced duct section, or a longer run than the quote assumed. Ask whether there is a return visit if the first pass does not clear the line, whether you get a written handoff, and whether they will say how often the vent should be checked again. If the answer to every question is a shrug, that tells you something too.
Where to look for names
The Local Help in St. Louis page is a reasonable place to start if you are looking for providers near your mother's home. Use it as a starting list, and still hold every name up against the questions above.
And while you are in the laundry room, ask your mother where the dryer lives. Some of us have not been back there since the last holiday.