Yes get another piggy - They absolutely must never be kept alone, they are highly social herd animals. No amount of human contact will ever make up for not having a friend . She may appear fine now but survival mode kicks in rather than thriving. And to spend the next up to 8 years alone would be awful for her. She absolutely will be 100% happier to have a friend.
The difference in cost of owning two rather than one is negligible - you will need a large cage (a minimum of 120cm x 60cm for two females, but the bigger the cage the happier the piggies are!) but the cost of hay and other veg isnāt going to dramatically increase. The only real financial difference is requiring enough in a vet fund for two piggies.
Please do not go by what you see on YouTube for how your bond with her will be - itās just not reality of how piggies are. They are prey animals, most donāt like being picked up and cuddled. For me, the joy in owning them actually comes from watching them socialise with their own kind, not through interaction with me. But keeping her alone will not make you bond with her any better, it wonāt make her friendlier, she may even become much more withdrawn and loneliness will eventually kick in for her.
When you get her a friend, you must do it the right way. Character compatibility and mutual liking is absolutely key, so daring at a rescue centre (when that is possible again) is the safest thing to do. Your piggy will choose her own friend which will result in a good bond, piggies health checked and sexed correctly. If you were to just go out and buy another one, then you have on no idea if the two piggies will be compatible, bondings can fail (and then youve got two single piggies in two separate cages), health issues can be brought in the missexing is common.
This collection of guides is great for new owners. Give them a read!
New Owners' Most Helpful How-To Guides and Information