I wouldn't start with sweet food. It will make accepting vegetables more difficult, especially strong tasting one . I would start like they do in France with soups. And dip the spoon in it, and have it just a bit dirtied. A soup without salt, homemade, not from a sachet or a can.
The WHO cannot discriminate between first and third world (where sanitation is an issue and to wean a baby clean water is important). Childhood gastric disease is a cause of death in Africa. The WHO cannot put a recommendation for UK and one for Sub-Saharan Africa, so it is a blanket, not before six months.
This said, gut maturation varies, some babies will have no issues at 4 months, other not so.
You have to think of the interest of the child first. Is she curious about food? does she follow the fork with her eyes from plate to mouth? You shouldn't start weaning because Auntie Jane says so, you do what is best for baby.
I suggest you buy https://www.goodreads.com/book/show/25159044-first-bite# it is not a cooking book but it will shape how to wean way better than trends and instagram accounts.
You have to think big and think ahead. What would you like her nutrition to be. What would you like her to eat growing up. The answer will hopefully be healthy food, fresh food, real food, curious and adventurous about food. So don't buy and never offer baby junk food, such as most of the supermarket "finger food" like melty puffs, rusks, baby cereal bars, veggie straw, ..... Careful around pouches and jars which offer sweet dominant food combination and thehigh heat high pressure processing creates a unique taste impossible to replicate. The taste of processed food. Do the test yourself. Buy a single veggie pouch and try it. Does it taste like the home made version? If it doesn't , she will never accept the homemade one. It is not a matter of does it nice, it is a matter off does it taste like the real one.
The main argument to start early is food acceptance which mostly vanishes around 8 months. So you have 4 months to make her like and enjoy broccoli, kale, peas, asparagus, fish (real one not battered) and so on.
Starting at 4 months to make her suck on a net to get some melon juice has no benefit. Just sugar, no fibre. The foods you will give her will also shape her gut microbiome. So think wisely.