I put a lot of tips on life in Nepal in my book Nepal: On a Budget, but is important to realize that Nepali are very easy to make friends with. They either like you because they think you have money and they can get some, they want to learn English or they may just want a tourist friend for the status. But they are very available for friendship. When you cull out the wolves from the herd you will find some really wonderful people. But remember wolves are everywhere and in Nepal they have some of the most inviting smiles and personalities. The other 90% are lovely.
But when you are my age in your late 50's and a female it can be more difficult. Most Nepali women in my age bracket do not speak English. Also, I don't think their husbands would like to have them hang with a woman who has abandoned her grown children and ran off all the way around the planet. My point is that you need a plan if you want to make good, compatible friends.
Here are a few suggestions:
If you belong to a fraternity, civic organization or support group check to see if they have a presence here. There is a Mosque, Catholic church, Lions Club, AA and NA. These are friends waiting for you to show up.
If you want to do any volunteer work check with your own embassy for some contacts. Anyone from your country with an NGO will be a good person to know and you can associate with them to meet volunteers from your country.
Join on line Traveler sites like this one. There are at least 10 of them, including the hosting sites.
If you go on a trek or some other activity solo, let the facilitator know you are alone so he can look for someone else who is either alone or open to adding someone to the group.
Eat at your own, or another guest house at meal times and try eating at the same one for a few days. You will start seeing familiar faces. Remember, it is always appropriate to invite other tourists to go exploring with you.
Check with your embassy for activities. Sometimes you can find parties and other networking settings there.
Smile and do all the other things.