I'm going to back up what was said mostly.
If participation is not mandatory, then there is usually no need to force a child into it. In general it's best to encourage but not bully a child into their actions at this stage, and that goes double if your child is also dealing with a partial language barriers that could further add stress and communication issues. A lack of spoken vocabulary can lead to an inability to communicate what she wants to the teacher, which can lead to her feeling frustrated and unheard and thus feeling she needs to resist even if the teacher is trying to understand. I've have had to deal with plenty of kids that were not very communicative or active in activities at this age, and ultimately I feel it's the job of the person caring for the child to work to get the kid engaged when that happens. In short, I'm inclined to believe the teacher is at fault.
The main question though is rather the actions your daughter is resisting are important that she engage in. In terms of the use of the restrooms that comes down to how likely an accident - or possible a disruption of class time to avoid an accident - is if she doesn't use the pottie. If she has only had one accident at school ever there is little evidence so far that failure to use the restrooms on demand is likely to lead to an accident, and thus in my mind little reason for a teacher to resort to such extreme measures to compel it. I feel the teacher should at least give your daughter a chance to prove herself by accepting a no.
Now if your daughter hasn't used the potty for many hours and is almost certainly about ready to explode then it may be worth pushing a bit harder for restroom use, but even then physically forcing her on the pottie is unlikely to work and can be counter productive. If, as I assume, there are frequent breaks and she is simply refusing to use the restroom on demand, for now the teacher should simply accept that and see if the child will use the restrooms at a later point, unless and until it's proven that not using it on the demand is going to lead to regular accidents.
As to not doing her 'activities' what are they? In most cases activities at this age are not that important to participate in. If she refuses every single learning opportunity that could be a problem, but even then if she is still working on mastering the language some leeway should be made. Generally the approach should again be to accept a no rather then force an action. At this age the child being comfortable and feeling she can express herself is more important then the learning in many ways. Her kindergarten is going to repeat anything she is being taught at this young an age anyways so unless she is going to have plenty of chances to learn the things their trying to teach her now.
You said you already spoke to the teacher and that's good. But going a little further on what I would suggest communicating, assuming my presumptions are right.
Let your daughter refuse to use the pottie until/unless she has proven there is a problem with using the restrooms or she has refused long enough that an accident is highly likely.
If your daughter really has gone so long that an accident is likely find a better way to compel use of the restrooms. Talk with the teacher about what you do when you think your daughter needs to use the restroom and she is not interested in doing so. Is there a carrot that can be offered instead of the stick, something that would make your daughter want to use the restrooms? Does praise or reward work well with her? Is there a restroom routine that works at home?
2b. Is the daughter using the potty if put on it? If this was a resistance thing then physically being put on the toilet shouldn't be enough to compel her to use it. I'd be looking to see if there is a different issue such as communication or daughter comfort level rather then defiance that is the main problem if she does use the restrooms once placed on them.
- Let daughter say no to activities unless she is actively getting in the way or causing problems for teacher or other students as a result. If no's continue to happen excessively and to the detriment of child's learning a separate talk should be had only after you're certain it's hindering education or you have gone awhile with daughter having no as an option and she continues to refuse at school to do things she would normally do at home.
3b. Ask more about how the refusal is happening and how daughter is responding to positive encouragement. How are the activities being offered, at this age most such 'activities' would usually be phrased as games or 'can you show me how to do this' rather then must do actions a child would have reason to get defiant on. If this is defiance then I'd want to know how the kid is being put into a position she feels a need to be defiant over such activities, if it isn't then I'd want to investigate if there are other reasons why she isn't participating.
3c. Depending on the severity of the language barrier, see if she will do anything in her native language. Can she count or say something in her primary language? The teacher likely doesn't know that much of the language, but picking up a handful of words to encourage the kid isn't that hard, in fact if it's a common enough language like Spanish the teacher likely already knows some of the basics. So for example if your daughter refuses to count in English (or whatever language) the teacher could ask if she wanted to count in her native language instead. The teacher can even say '[daughter] I don't know how to count in [language], can you teach me?' or something along those lines which will avoid needing to know the language while also giving daughter reason to feel special for knowing a second language and thus motive to show off what she knows. You might want your daughter to master the other language, but if she is surrounded by it all day at school I'm confident she will pick it up regardless so occasionally getting to use her primary language as encouragement to participate shouldn't do any serious harm.