There are about a gazillion types of ants known to science and probably about two gazillion types they haven't noticed yet. But for the sake of a simple answer, I'll divide them into the three most important types: ants who love wood chips, ants who love plants, and and ants who don't care about either. The ones in the first category love wood chips and/or other dead vegetation for food and/or housing. They may be attracted by wood chips, but most ants in this category are beneficial in breaking down dead vegetation for your vegies to get the nutrients. The ones in the second category use plants for food and/or shelter. Some of these guys "farm" aphids. They may be attracted to your garden by the vegies themselves, regardless of the mulch. The third category will be there regardless of the vegies or mulch. Some of these ants are beneficial hunters of other insects. These categories overlap a bit, but are generally true. The science guys are a lot farther ahead with describing and naming insects, than they are with figuring out how they live and what they eat. If you look in a real deal scientific book on insects, they identify all those tiny red and black ants by things like what their mandibles (jaws) or antennae (feelers) look like when magnified. Just watching them gives you more practical info than going through all that to get a Latin name and no details. Wood chips near the porch may be bad for two reasons. First, the wood chips will shrink a lot as they decompose. second, I've read that they attract termites and carpenter ants, which you don't want damaging your house. My personal experience is that they are only interested in larger pieces of wood that they can create a nest in, and not chips or saw dust. It may be an old wives tale from people seeing carpenter ants in wood chips and/or saw dust where trees were removed and not realizing that they were really living in the stump or underground roots. In your area it may be different though. Ziggy

I prefer shredded hardwood mulch for flower beds. It has a nice uniform appearance and will break down and enrich the soil. As it breaks down, no need to rake up the remains-- just plan to add a new layer (usually in the fall). :Pinebark mulch is great for acid-loving shrubs like gardenias and azaleas but it's typically more expensive. If your old mulch cakes up and forms a crust, you can break it up with a rake or hoe and turn it into the soil. This happens with some mulches and also if the original mulch is laid a little too thick. Wood chip is not as good for suppressing weeds but I like it fine for tree rings and shrub borders. In the arboretum where I volunteer we use lots of both, just for different purposes. In our demonstration vegetable garden we mulch with grass clipping and straw with a layer of newspaper underneath!

Lots of possible reasons - shallow fibrous roots sucking out moisture and nutrients, or shade as you mentioned.

first.. its her garden.. and if it makes her happy.. good for her ... wood chips are a weed suppressor ... and she is putting basically soil.. over it.. whats that all about .... sorta defeats the purpose .. imo ... next.. by adding what is a fert on some level.. only around the plants .. one might speculate.. that she is calling the tree roots.. to her plants ... been there.. done that.. not a great long term idea ... so ... all you are left with.. is if you want to destroy her happiness with your opinion about it all .. i say.. smile.. nod.. and keep your opinion to yourself.. lol ... unless she asks ... ken