Well, that depends. If your ralts had never met these trainers, she may be exhibiting her species’ signature shyness. If that’s the case, then it’s important to work with her and get her used to spending time around people other than you. Doing this involves a process similar to getting a pokémon acclimated to a new environment or a new teammate: start off gradually (perhaps by introducing her to only one or two friends) and work your way up until she can handle more.
If she seems disgruntled towards these trainers, however, or if this is a sudden change in behavior, then there are two possibilities for what might be going on. First, it’s possible that your ralts is experiencing jealousy. Members of the ralts family are some of the most loyal pokémon in existence, so they’re extremely protective and sometimes possessive of their trainers. It’s not unusual for a ralts to become aggressive towards other humans they feel are jeopardizing their relationship with their trainers. If this is the case, it’s important to explain to your ralts that your relationship with her isn’t going to change just because you’ve met new people. I would recommend increasing the amount of time you spend training her or giving her a bit more affection than usual to reinforce this.
The second option, meanwhile, is that there is something very wrong with the trainers you’ve befriended. Remember that members of the ralts line are talented empaths and can thus sense when someone is not being entirely truthful to you. If your ralts is reacting to specific friends or if she seems on edge as she teleports away, it’s important to communicate with her and try to determine what she’s detected. From there, you may be able to determine the best course of action, whether it’s reassuring your ralts that your new friends are trustworthy or taking action to distance yourself from potentially toxic people.
Whatever you do, anonymous, communication and observation are the keys. Pay attention not only to what your ralts is doing in general but also her body language and any other signal she may be sending you.
Best of luck!