Whatever you looked at that advised nappy changing away from others as a means of teaching bodily privacy got it all wrong. A 2.5 year old simply cannot understand the concept of bodily privacy.
What you can do is teach the correct names for the bodily parts - no twee names for penis, anus, vulva, clitoris or vagina. Say these words out loud yourself without flinching. Teach your DD when she asks.
At about 3 or 4 you can introduce the idea of the swimsuit zones. These are the bodily privacy zones. Under no circumstances can a child be given the impression that they are responsible if someone breaches these zones. These lessons are taught in conjunction with instructions on secrets - that there are no secrets at all from mum and dad, that any adult who asks you to keep a secret is up to no good and while you can agree to keep something secret you do not have to keep it secret. Also that mum and dad will never get angry with you no matter what you tell them and no matter what someone else may have told her about you.
For a 2 year old, it's more important to teach that they don't have to hug or kiss anyone including dad or mum or gran or grandad or uncle, cousin, brother, sister, etc. if they don't want to, or sit on anyone's knee, etc.
It's important that you respect a No from your child even at the risk of putting the nose of another adult out of joint. Don't smile or grin or giggle when you back up your child, or offer an explanation that includes the child having a grumpy day/off day/a cold/tired, whatever. The other adult can take offense or shrug or have whatever response they wish - it is not up to you to manage their response, and it is dangerous to imply a criticism of the child by offering an explanation that makes their response seem out of place or requiring an explanation.
The big issue that you can teach a 2 year old is consent. This can be done in a variety of ways.
You can let them have a few choices of what to wear daily so they get a sense of power and control over their own life. Don't make them wear a hat even on a cold day but bring one for when they change their mind. Offer a few choices of lunch or breakfast. Respect it if they don't want to eat much or if they want more.
It's important that you step in and stop any roughhousing that goes on in your house and in the houses of others to the point where one child is feeling upset, and to make your house a no tickling zone. Stop any playing with hair if one child doesn't like it. Stop any unwanted physical play as soon as one child objects.
Treat the child with respect - if you feel you have been wrong about something, tell them you are sorry. Ask for their opinion on things. Have conversations. Tell them ahead of time when they will have to stop playing and get ready to do something else (running errands, whatever) - no swooping in and plucking them up and expecting them to go along with your plans with no questions asked. Be patient with objections. Try to strike deals to get things done. Be patient with what might be perceived as 'backtalk'. Try to tease out the emotion behind behaviour like whining or tantrums instead of clamping down on it. Explain that we can say 'No thank you' instead of throwing our bowl on the floor.
The overall aim is to give your child the impression that she will be listened to.